This paper continues the recent research of the author, with application to 3D computational flui... more This paper continues the recent research of the author, with application to 3D computational fluid dynamics multicriterial optimization of turbomachinery parts. Computational Fluid Dynamics has been an ubicuous tool for compressor design for decades, helping the designers to test the aerodynamic parameters of their machines with great accuracy. Due to advances of multigrid methods and the improved robustness of structured solvers, CFD can nowadays be part of an optimization loop with artificial neural networks or evolutive algorithms. This paper presents a case study of an air centrifugal compressor rotor optimized using Numeca's Design 3D CFD suite. The turbulence model used for the database generation and the optimization stage is Spalart Allmaras. Results indicate a fairly quick convergence time per individual as well as a good convergence of the artificial neural network optimizer.
The main objective of the current paper is to establish an optimal configuration for a micro gas ... more The main objective of the current paper is to establish an optimal configuration for a micro gas turbine, component of a combined heat and power (CHP) system. The design and modeling of the turbine rotor were achieved using CAE/CAD software. This paper will focus mainly on identifying issues regarding the mechanical resistance of the radial turbine. In order to increase the safety factor, a brief analysis of the designing mechanical stages was necessary. The CAD model for the optimal impeller was realized considering the facilitation of its manufacturing process and maintenance. The analysis is based on finite element method, implemented in NASTRAN. The characteristics of the material used are the following: density 8180 kg/m3, 1.67E11 N/m2 and υ = 0.28, for an angular velocity of 40 000 rpm. The presented paper aims to determine a functional configuration for gas turbine’s impellers, in order to effectively manage to deal with the conditions of temperature and mechanical stresses resulted in the exploitation of a CHP gas turbine. This objective was achieved after iteratively designing multiple configurations.
The present paper presents the numerical analysis for a transonic centrifugal compressor using st... more The present paper presents the numerical analysis for a transonic centrifugal compressor using steady state CFD. The blade tip clearance effect over the position of shock waves, tip losses and the performances of the impeller are studied. Numerical simulations have been performed using RANS modelling, with the k-omega SST turbulence model (Shear Stress Transport). Eight cases were taken into consideration for the impeller with the following blade tip clearances values: 0 mm, 0.1 mm, 0.3 mm, 0.4 mm, 0.5mm, 0.7 mm, 1 mm, 2 mm, at the same operating conditions. For the entire stage only seven cases were studied, without the value for 0.1 mm because of its abnormal behaviour, as can be seen in the case of the impeller simulations. Results showed that the position of the shock wave does not change with the increase of the tip clearance. Aerodynamic losses due to shock wave, secondary flow and turbulence can be seen in the polytropic efficiency of the centrifugal impeller and the difference between the two extreme cases is about 3.2 %.
Zenodo (CERN European Organization for Nuclear Research), Feb 12, 2017
In this paper computational fluid dynamics is used to provide a proof of concept for controlled f... more In this paper computational fluid dynamics is used to provide a proof of concept for controlled flow separation using thermal wall interactions with the velocity boundary layer. A 3D case study is presented, using a transition modeling Shear Stress Transport turbulence model. The highly loaded single slot flap airfoil was chosen to be representative for a light aircraft and the flow conditions were modeled after a typical landing speed. In the baseline case, adiabatic walls were considered while in the separation control case, the top surface of the flaps was heated to 500 K. This heating lead to flow separation on the flaps and a significant alteration of the flow pattern across all the elements of the wing. The findings indicate that this control method has potential, with implications in both aeronautical as well as sports and civil engineering applications.
Research interest regarding micro turbines has improved, as their development and manufacturing i... more Research interest regarding micro turbines has improved, as their development and manufacturing increased due to the rapid expansion of their application range, from military applications to civil ones. This paper aims to present the methodology used for the ascertainment of the optimal configuration for the functional parameters of a micro jet engine, using a mathematical model for the evaluation of the Brayton cycle as well as a commercial software for its investigation. The DevJet micro jet engine is developed for a thrust of 80 daN with an estimated rotational speed of 40,000 rpm. An analytical model of the Brayton cycle for the evaluation of the main parameters of interest is employed and twelve variants are evaluated, considering values for the pressure ratio ranging from 4 and up to 5, while the maximum temperature range is between 1,050 K and 1,200 K. The optimal variant is selected, and the data is transferred to the commercial software GasTurb in order to generate the diagram of the thermodynamic cycle. The outcome of this research paper represents the input data for the 3D modelling and numerical simulation of the main systems of the micro jet engine.
The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and th... more The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and the same airfoil with heated patches. Both suction and pressure sides were divided into two regions covering the leading edge (L.E.) and trailing edge (T.E.). A RANS method sensitivity test has been performed in the preliminary stage while for the extended 3D cases a DES-SST approach was used. Results indicate that surface temperature distribution influences the aerodynamics of the airfoil, in particular the viscous drag component but also the lift of the airfoil. Moreover, the influence depends not only on the surface temperature but also on the positioning of the heated surfaces, particularly in the case of pressure lift and drag. Further work will be needed to optimize the temperature distribution for airfoil with higher camber.
This paper addresses the problem of obtaining a set of mathematical equations that can accurately... more This paper addresses the problem of obtaining a set of mathematical equations that can accurately describe the velocity flow field near a cylindrical surface influenced by the Coandă effect. The work is relevant since the current state of the art Reynolds Averaged Navier Stokes models with curvature correction do not completely describe the properties of the flow in accordance with the experimental data. Semi-empirical equations are therefore deduced based on experimental and theoretical state of the art. The resulting model is validated over a wider range of geometric layouts than any other existing semi-empirical model of its kind. The applications of this model are numerous, from super circulation wing calculations to fluidic devices such as actuators or fluidic diodes.
Journal of Marine Science and Engineering, Feb 1, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at h... more Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at highvelocity to generate thrust. This paper proposes the use of the quantum pair formation for generating a working mass, this is different than conventional anti-matter thrusters since the material particles generated are used as a propellant mass not as energy storage. Two thrusters will be compared: photonic and quantum pair generation. The latter will be shown to offer better momentum than photons above certain energy levels. The implication is that quantum pair thrusters may develop into a new class of space propulsion systems. Keywords: quantum pair formation, space propulsion, photonic propulsion
The paper addresses the issue of thin jets subjected to the Coandă effect and in particular the b... more The paper addresses the issue of thin jets subjected to the Coandă effect and in particular the boundary layer modeling. An existing semi-empirical Coandă effect mathematical model is modified, with a more complex boundary layer model, in order to allow the estimative calculation of the detachment point and of other parameters such as friction coefficients, wall shear stress and the momentum and displacement integral thicknesses. The method used is analytical, based on the Rodman-Wood-Roberts model and the Pohlhausen boundary layer method. The work is significant for the pre-design calculations as well as for a quick checking of RANS CFD simulation results.
In this paper a case study of a trans-sonic centrifugal compressor at various tip gap values is p... more In this paper a case study of a trans-sonic centrifugal compressor at various tip gap values is presented. At all clearance values, global parameters of efficiency and head coefficient were assessed for the rotor and the stage. All results were obtained through 3D CFD simulations carried out with the k-omega SST model. Results indicate that stage performance can easily be correlated with the tip gap size while rotor performances appear to be subject to more complex interactions. The work may be used to validate and extend the state of the art correlations and also to pave the way for more in-depth analysis into the phenomena occurring in centrifugal compressor flows.
The term supercirculation refers to an active, fluidic circulation control method used for a vari... more The term supercirculation refers to an active, fluidic circulation control method used for a variety of aeronautical applications. In particular, this paper refers to supercirculation of entrainment wings. Using experimental data as well as some basic analytical equations, a mathematical expression is used to define supercirculation; subsequently an optimization calculation is provided for the minimal blowing pressure ratio needed for achieving supercirculation. Also, based on the proposed definition, a screening equation is determined in order to discern whether or not a certain airfoil has a geometry suited for supercirculation.
The current paper refers to the preliminary estimation of the Reynolds number for curved wall jet... more The current paper refers to the preliminary estimation of the Reynolds number for curved wall jets. This, in turn, can be a useful tool for controlling the boundary layer mesh size near a generic curved wall which is wetted by a thin, attached jet. The method relies on analytical calculations that link the local curvature of the wall with the pressure gradient and further, the local Reynolds number. Knowing the local Reynolds number distribution, a CFD user can tailor their mesh size to more exact specifications (e.g. y+=1 for k-omega RANS models) and lower the risk that the mesh is too coarse or finer than necessary.
Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at h... more Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at highvelocity to generate thrust. This paper proposes the use of the quantum pair formation for generating a working mass, this is different than conventional anti-matter thrusters since the material particles generated are used as a propellant mass not as energy storage. Two thrusters will be compared: photonic and quantum pair generation. The latter will be shown to offer better momentum than photons above certain energy levels. The implication is that quantum pair thrusters may develop into a new class of space propulsion systems. Keywords: quantum pair formation, space propulsion, photonic propulsion
2018 5th International Conference on Mathematics and Computers in Sciences and Industry (MCSI), 2018
In this scientific paper, a numerical analysis was performed to determine the performances of an ... more In this scientific paper, a numerical analysis was performed to determine the performances of an oil-injected screw compressor operating at high pressures. For this analysis was defined the computing domain composed from five subdomains, two rotors represented by the male rotor and the female rotor and three stators representing the suction side, pressure side and oil inlet subdomain. To generate the meshes for rotating domains we use the TwinMesh commercial software, dedicated software for positive-displacement volumetric machines. For flow modeling the Ansys CFX CFD software with The SST turbulence model was used. The analysis was unsteady and a subroutine done in Fortran was used for grids import. The results of this analysis are evaluated by looking at gas and oil massflow variations, power consumption and torque value for each rotor.
International journal of mechanical engineering, Sep 25, 2017
The present paper describes the numerical analysis of the fluid flow around a finite span wing, N... more The present paper describes the numerical analysis of the fluid flow around a finite span wing, NACA 0012 profile, provided with an aileron, placed at three static positions, corresponding to three different angles. The numerical simulation has been made with the commercial software ANSYS Fluent. The study is conducted in the case of the unsteady regime, the turbulence model used is SST k-ω, and the filtering of the governing equations is carried out under the DES (Detached Eddy Simulation) approach. The results show that the aileron position and velocity influences the flow and are leading to an aerodynamic instability at the trailing edge of the aileron, in some cases also influencing the wing end.
The current paper concerns the development of a very high pressure ratio single stage centrifugal... more The current paper concerns the development of a very high pressure ratio single stage centrifugal compressor. Several research questions: assessing the design point of the impeller, behavior towards stall and surge as well as the turbulence model sensitivity under RANS assumptions. Three turbulence models, k-omega SST, Spalart Allmaras RC and Reynolds Stress Model, were assessed over the design speedline through a grid sensitivity test. All grids maintain the same first cell size, insuring a y+<1 and are fully conformal in order to minimize artificial entropy and interface reflexions. Findings show that mesh convergence depends highly on the operating point, with increased density being needed close to choke. Near stall, the behavior depends significantly on the averaging method for the outlet parameters, particularly due to flow patterns emerging from the very shallow tangential streamlines. The paper sets the scene for more elaborate simulations such as DES or URANS helping make decisions on the meshing strategy and turbulence modeling for modern day centrifugal compressors.
Several studies present how serrated rotor blades mix wakes in order to attenuate noise levels. T... more Several studies present how serrated rotor blades mix wakes in order to attenuate noise levels. The current paper analyses how this geometry, applied on the trailing edge, affects the global parameters of a transonic axial compressor impeller. Innovative solutions tackling the rotor-stator interaction mechanism in an axial compressor for noise reduction include serrated trailing edges. Inspired by chevron nozzles, serrations can be transferred to the open-rotor concept in order to reduce tonal noise. Throughout the study we will be focusing on aerodynamic loss estimation while being mindful of the mechanisms which lead to rotor-stator interaction noise, without assessing its per-se effectiveness for noise mitigation. Owing to its qualitative experimental data availability, NASA's Rotor 37 was chosen as a baseline. A set of fully viscous 3D simulations, using the SST k-omega turbulence model and RANS, was carried out to this effect. Spatial discretization was made using a fully structured pre-mesh in order to optimize resolution and accelerate convergence. Fullfactorial samples were generated for the geometric variations in order to capture the aerodynamic implications of this concept. Overall, the analysed case provides promising perspectives, pending optimization studies and experimental tests thereof.
Supersonic flight has become a practical reality since the 1950s. One of the first ways to study ... more Supersonic flight has become a practical reality since the 1950s. One of the first ways to study high speed effects of the shock waves is to evaluate the aerodynamic coefficients of an airfoil. The work described herein refers to a series of 2.5D LES numeric simulations, to investigate the behavior of the shock wave on the airfoil. To reduce the unwanted effects, a porous surface is placed on 80% of suction and pressure side of a NACA 0012 airfoil. Solving the motion equations was carried out with Ansys Fluent. Qualitative comparison consists in the pressure contours visualization for different angles of attack, showing how shock waves form on the airfoil surfaces. After plotting the polar diagrams, CL = f(AoA) and CL = f(CD), a quantitative comparison was made between the baseline airfoil and the same airfoil but with porous media on each surface side.
Zenodo (CERN European Organization for Nuclear Research), Aug 26, 2016
Revamping of industrial turbo-machinery is commonplace in the oil and gas industry in application... more Revamping of industrial turbo-machinery is commonplace in the oil and gas industry in applications where subterranean combustion is used for oil extraction. The current case study refers to such an industrial compressor revamping , using a state of the art 3D fully viscous CFD methodology coupled with artificial neural networks (ANNs) and genetic algorithms (GA). The ANN is used to establish correlations within a database of CFD simulations of geometrical variations of the original rotor and the GA uses those correlations to estimate an optimum. The estimate is then tested with the same CFD method and the results are fed back into the database, increasing the accuracy of the ANN correlations. The process is reiterated until the optimum estimated by the GA is confirmed with the CFD simulations. The resulting geometry is superior to the original in terms of efficiency and pressure ratio as well as the range of stabile operation, as confirmed by the successful implementation in the field. In this paper we present an analysis of why the optimized geometry achieves superior performances to the original one. Further work will present comparison between the detailed experimental data and CFD.
This paper continues the recent research of the author, with application to 3D computational flui... more This paper continues the recent research of the author, with application to 3D computational fluid dynamics multicriterial optimization of turbomachinery parts. Computational Fluid Dynamics has been an ubicuous tool for compressor design for decades, helping the designers to test the aerodynamic parameters of their machines with great accuracy. Due to advances of multigrid methods and the improved robustness of structured solvers, CFD can nowadays be part of an optimization loop with artificial neural networks or evolutive algorithms. This paper presents a case study of an air centrifugal compressor rotor optimized using Numeca's Design 3D CFD suite. The turbulence model used for the database generation and the optimization stage is Spalart Allmaras. Results indicate a fairly quick convergence time per individual as well as a good convergence of the artificial neural network optimizer.
The main objective of the current paper is to establish an optimal configuration for a micro gas ... more The main objective of the current paper is to establish an optimal configuration for a micro gas turbine, component of a combined heat and power (CHP) system. The design and modeling of the turbine rotor were achieved using CAE/CAD software. This paper will focus mainly on identifying issues regarding the mechanical resistance of the radial turbine. In order to increase the safety factor, a brief analysis of the designing mechanical stages was necessary. The CAD model for the optimal impeller was realized considering the facilitation of its manufacturing process and maintenance. The analysis is based on finite element method, implemented in NASTRAN. The characteristics of the material used are the following: density 8180 kg/m3, 1.67E11 N/m2 and υ = 0.28, for an angular velocity of 40 000 rpm. The presented paper aims to determine a functional configuration for gas turbine’s impellers, in order to effectively manage to deal with the conditions of temperature and mechanical stresses resulted in the exploitation of a CHP gas turbine. This objective was achieved after iteratively designing multiple configurations.
The present paper presents the numerical analysis for a transonic centrifugal compressor using st... more The present paper presents the numerical analysis for a transonic centrifugal compressor using steady state CFD. The blade tip clearance effect over the position of shock waves, tip losses and the performances of the impeller are studied. Numerical simulations have been performed using RANS modelling, with the k-omega SST turbulence model (Shear Stress Transport). Eight cases were taken into consideration for the impeller with the following blade tip clearances values: 0 mm, 0.1 mm, 0.3 mm, 0.4 mm, 0.5mm, 0.7 mm, 1 mm, 2 mm, at the same operating conditions. For the entire stage only seven cases were studied, without the value for 0.1 mm because of its abnormal behaviour, as can be seen in the case of the impeller simulations. Results showed that the position of the shock wave does not change with the increase of the tip clearance. Aerodynamic losses due to shock wave, secondary flow and turbulence can be seen in the polytropic efficiency of the centrifugal impeller and the difference between the two extreme cases is about 3.2 %.
Zenodo (CERN European Organization for Nuclear Research), Feb 12, 2017
In this paper computational fluid dynamics is used to provide a proof of concept for controlled f... more In this paper computational fluid dynamics is used to provide a proof of concept for controlled flow separation using thermal wall interactions with the velocity boundary layer. A 3D case study is presented, using a transition modeling Shear Stress Transport turbulence model. The highly loaded single slot flap airfoil was chosen to be representative for a light aircraft and the flow conditions were modeled after a typical landing speed. In the baseline case, adiabatic walls were considered while in the separation control case, the top surface of the flaps was heated to 500 K. This heating lead to flow separation on the flaps and a significant alteration of the flow pattern across all the elements of the wing. The findings indicate that this control method has potential, with implications in both aeronautical as well as sports and civil engineering applications.
Research interest regarding micro turbines has improved, as their development and manufacturing i... more Research interest regarding micro turbines has improved, as their development and manufacturing increased due to the rapid expansion of their application range, from military applications to civil ones. This paper aims to present the methodology used for the ascertainment of the optimal configuration for the functional parameters of a micro jet engine, using a mathematical model for the evaluation of the Brayton cycle as well as a commercial software for its investigation. The DevJet micro jet engine is developed for a thrust of 80 daN with an estimated rotational speed of 40,000 rpm. An analytical model of the Brayton cycle for the evaluation of the main parameters of interest is employed and twelve variants are evaluated, considering values for the pressure ratio ranging from 4 and up to 5, while the maximum temperature range is between 1,050 K and 1,200 K. The optimal variant is selected, and the data is transferred to the commercial software GasTurb in order to generate the diagram of the thermodynamic cycle. The outcome of this research paper represents the input data for the 3D modelling and numerical simulation of the main systems of the micro jet engine.
The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and th... more The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and the same airfoil with heated patches. Both suction and pressure sides were divided into two regions covering the leading edge (L.E.) and trailing edge (T.E.). A RANS method sensitivity test has been performed in the preliminary stage while for the extended 3D cases a DES-SST approach was used. Results indicate that surface temperature distribution influences the aerodynamics of the airfoil, in particular the viscous drag component but also the lift of the airfoil. Moreover, the influence depends not only on the surface temperature but also on the positioning of the heated surfaces, particularly in the case of pressure lift and drag. Further work will be needed to optimize the temperature distribution for airfoil with higher camber.
This paper addresses the problem of obtaining a set of mathematical equations that can accurately... more This paper addresses the problem of obtaining a set of mathematical equations that can accurately describe the velocity flow field near a cylindrical surface influenced by the Coandă effect. The work is relevant since the current state of the art Reynolds Averaged Navier Stokes models with curvature correction do not completely describe the properties of the flow in accordance with the experimental data. Semi-empirical equations are therefore deduced based on experimental and theoretical state of the art. The resulting model is validated over a wider range of geometric layouts than any other existing semi-empirical model of its kind. The applications of this model are numerous, from super circulation wing calculations to fluidic devices such as actuators or fluidic diodes.
Journal of Marine Science and Engineering, Feb 1, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at h... more Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at highvelocity to generate thrust. This paper proposes the use of the quantum pair formation for generating a working mass, this is different than conventional anti-matter thrusters since the material particles generated are used as a propellant mass not as energy storage. Two thrusters will be compared: photonic and quantum pair generation. The latter will be shown to offer better momentum than photons above certain energy levels. The implication is that quantum pair thrusters may develop into a new class of space propulsion systems. Keywords: quantum pair formation, space propulsion, photonic propulsion
The paper addresses the issue of thin jets subjected to the Coandă effect and in particular the b... more The paper addresses the issue of thin jets subjected to the Coandă effect and in particular the boundary layer modeling. An existing semi-empirical Coandă effect mathematical model is modified, with a more complex boundary layer model, in order to allow the estimative calculation of the detachment point and of other parameters such as friction coefficients, wall shear stress and the momentum and displacement integral thicknesses. The method used is analytical, based on the Rodman-Wood-Roberts model and the Pohlhausen boundary layer method. The work is significant for the pre-design calculations as well as for a quick checking of RANS CFD simulation results.
In this paper a case study of a trans-sonic centrifugal compressor at various tip gap values is p... more In this paper a case study of a trans-sonic centrifugal compressor at various tip gap values is presented. At all clearance values, global parameters of efficiency and head coefficient were assessed for the rotor and the stage. All results were obtained through 3D CFD simulations carried out with the k-omega SST model. Results indicate that stage performance can easily be correlated with the tip gap size while rotor performances appear to be subject to more complex interactions. The work may be used to validate and extend the state of the art correlations and also to pave the way for more in-depth analysis into the phenomena occurring in centrifugal compressor flows.
The term supercirculation refers to an active, fluidic circulation control method used for a vari... more The term supercirculation refers to an active, fluidic circulation control method used for a variety of aeronautical applications. In particular, this paper refers to supercirculation of entrainment wings. Using experimental data as well as some basic analytical equations, a mathematical expression is used to define supercirculation; subsequently an optimization calculation is provided for the minimal blowing pressure ratio needed for achieving supercirculation. Also, based on the proposed definition, a screening equation is determined in order to discern whether or not a certain airfoil has a geometry suited for supercirculation.
The current paper refers to the preliminary estimation of the Reynolds number for curved wall jet... more The current paper refers to the preliminary estimation of the Reynolds number for curved wall jets. This, in turn, can be a useful tool for controlling the boundary layer mesh size near a generic curved wall which is wetted by a thin, attached jet. The method relies on analytical calculations that link the local curvature of the wall with the pressure gradient and further, the local Reynolds number. Knowing the local Reynolds number distribution, a CFD user can tailor their mesh size to more exact specifications (e.g. y+=1 for k-omega RANS models) and lower the risk that the mesh is too coarse or finer than necessary.
Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at h... more Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle at highvelocity to generate thrust. This paper proposes the use of the quantum pair formation for generating a working mass, this is different than conventional anti-matter thrusters since the material particles generated are used as a propellant mass not as energy storage. Two thrusters will be compared: photonic and quantum pair generation. The latter will be shown to offer better momentum than photons above certain energy levels. The implication is that quantum pair thrusters may develop into a new class of space propulsion systems. Keywords: quantum pair formation, space propulsion, photonic propulsion
2018 5th International Conference on Mathematics and Computers in Sciences and Industry (MCSI), 2018
In this scientific paper, a numerical analysis was performed to determine the performances of an ... more In this scientific paper, a numerical analysis was performed to determine the performances of an oil-injected screw compressor operating at high pressures. For this analysis was defined the computing domain composed from five subdomains, two rotors represented by the male rotor and the female rotor and three stators representing the suction side, pressure side and oil inlet subdomain. To generate the meshes for rotating domains we use the TwinMesh commercial software, dedicated software for positive-displacement volumetric machines. For flow modeling the Ansys CFX CFD software with The SST turbulence model was used. The analysis was unsteady and a subroutine done in Fortran was used for grids import. The results of this analysis are evaluated by looking at gas and oil massflow variations, power consumption and torque value for each rotor.
International journal of mechanical engineering, Sep 25, 2017
The present paper describes the numerical analysis of the fluid flow around a finite span wing, N... more The present paper describes the numerical analysis of the fluid flow around a finite span wing, NACA 0012 profile, provided with an aileron, placed at three static positions, corresponding to three different angles. The numerical simulation has been made with the commercial software ANSYS Fluent. The study is conducted in the case of the unsteady regime, the turbulence model used is SST k-ω, and the filtering of the governing equations is carried out under the DES (Detached Eddy Simulation) approach. The results show that the aileron position and velocity influences the flow and are leading to an aerodynamic instability at the trailing edge of the aileron, in some cases also influencing the wing end.
The current paper concerns the development of a very high pressure ratio single stage centrifugal... more The current paper concerns the development of a very high pressure ratio single stage centrifugal compressor. Several research questions: assessing the design point of the impeller, behavior towards stall and surge as well as the turbulence model sensitivity under RANS assumptions. Three turbulence models, k-omega SST, Spalart Allmaras RC and Reynolds Stress Model, were assessed over the design speedline through a grid sensitivity test. All grids maintain the same first cell size, insuring a y+<1 and are fully conformal in order to minimize artificial entropy and interface reflexions. Findings show that mesh convergence depends highly on the operating point, with increased density being needed close to choke. Near stall, the behavior depends significantly on the averaging method for the outlet parameters, particularly due to flow patterns emerging from the very shallow tangential streamlines. The paper sets the scene for more elaborate simulations such as DES or URANS helping make decisions on the meshing strategy and turbulence modeling for modern day centrifugal compressors.
Several studies present how serrated rotor blades mix wakes in order to attenuate noise levels. T... more Several studies present how serrated rotor blades mix wakes in order to attenuate noise levels. The current paper analyses how this geometry, applied on the trailing edge, affects the global parameters of a transonic axial compressor impeller. Innovative solutions tackling the rotor-stator interaction mechanism in an axial compressor for noise reduction include serrated trailing edges. Inspired by chevron nozzles, serrations can be transferred to the open-rotor concept in order to reduce tonal noise. Throughout the study we will be focusing on aerodynamic loss estimation while being mindful of the mechanisms which lead to rotor-stator interaction noise, without assessing its per-se effectiveness for noise mitigation. Owing to its qualitative experimental data availability, NASA's Rotor 37 was chosen as a baseline. A set of fully viscous 3D simulations, using the SST k-omega turbulence model and RANS, was carried out to this effect. Spatial discretization was made using a fully structured pre-mesh in order to optimize resolution and accelerate convergence. Fullfactorial samples were generated for the geometric variations in order to capture the aerodynamic implications of this concept. Overall, the analysed case provides promising perspectives, pending optimization studies and experimental tests thereof.
Supersonic flight has become a practical reality since the 1950s. One of the first ways to study ... more Supersonic flight has become a practical reality since the 1950s. One of the first ways to study high speed effects of the shock waves is to evaluate the aerodynamic coefficients of an airfoil. The work described herein refers to a series of 2.5D LES numeric simulations, to investigate the behavior of the shock wave on the airfoil. To reduce the unwanted effects, a porous surface is placed on 80% of suction and pressure side of a NACA 0012 airfoil. Solving the motion equations was carried out with Ansys Fluent. Qualitative comparison consists in the pressure contours visualization for different angles of attack, showing how shock waves form on the airfoil surfaces. After plotting the polar diagrams, CL = f(AoA) and CL = f(CD), a quantitative comparison was made between the baseline airfoil and the same airfoil but with porous media on each surface side.
Zenodo (CERN European Organization for Nuclear Research), Aug 26, 2016
Revamping of industrial turbo-machinery is commonplace in the oil and gas industry in application... more Revamping of industrial turbo-machinery is commonplace in the oil and gas industry in applications where subterranean combustion is used for oil extraction. The current case study refers to such an industrial compressor revamping , using a state of the art 3D fully viscous CFD methodology coupled with artificial neural networks (ANNs) and genetic algorithms (GA). The ANN is used to establish correlations within a database of CFD simulations of geometrical variations of the original rotor and the GA uses those correlations to estimate an optimum. The estimate is then tested with the same CFD method and the results are fed back into the database, increasing the accuracy of the ANN correlations. The process is reiterated until the optimum estimated by the GA is confirmed with the CFD simulations. The resulting geometry is superior to the original in terms of efficiency and pressure ratio as well as the range of stabile operation, as confirmed by the successful implementation in the field. In this paper we present an analysis of why the optimized geometry achieves superior performances to the original one. Further work will present comparison between the detailed experimental data and CFD.
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