يارب دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا : Please cite this article using: M. R. Ansar... more يارب دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا : Please cite this article using: M. R. Ansari, E. Salimi, B. Habibpour, P. Adibi, Numerical simulation and investigation of bubble velocity and deformation in inclined channel with two consecutive slopes using VOF-PLIC method, Modares Mechanical Engineering, Vol. 14, No. 11, pp. 29-36, 2014 (In Persian) هیبش بیش لاناک رد بابح لکش رییغت و تعرس یسررب و يددع يزاس بیش ود اب راد
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Dec 6, 2021
The flow around a circular-cone is 3D, unsteady and turbulent. As reported in many research works... more The flow around a circular-cone is 3D, unsteady and turbulent. As reported in many research works on this type of flow, boundary layer separations, vortex structures and the effect of surface roughness are strongly related. The effect of roughness is still not completely understood and proves challenging both for numerical and experimental approaches. The present work aims to gain more insights in understanding and numerically predicting this type of flows. Particularly, it attempts to improve the accuracy of numerical predictions of the effects of roughness on the asymmetric vortex flow around a circular-cone at subsonic flow conditions. This is performed using numerical simulations, which predict the flow field details across different transversal stations along the cone. Therefore, we have analyzed the effect of many turbulence models, notably, the transition SST, using ANSYS Fluent code. Flows characteristics are highlighted and validated against the well-known theory and some experimental measurements. The findings depict that a surface roughness height about 0.32 mm has efficaciously triggered the boundary layer to change from a laminar to a fully turbulent state in both sides of the body, in addition to a significant reduction in the global lateral force. Moreover, it seems that the roughness reduces the asymmetry of the vortex in the leeward side of the cone. Testing many roughness heights has allowed us to determine the way in which it is possible to reduce the side force effectively at high angles of attack without affecting the lift of the cone cylinder.
We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the ... more We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the short-period transiting hot Jupiter system WASP-19b with a single joint fit to photometric data and resolve parameter degeneracy. We analyze data taken by the Transiting Exoplanet Survey Satellite (TESS) during sectors 9 and 36. We model the data with our five-component model: primary transit, secondary eclipse, ellipsoidal variations, thermal emission, and reflected light, which are jointly fit to extract the information from all parameters simultaneously. The amplitude of Doppler beaming was also estimated to be ∼3 parts-per-million (ppm), but given the precision of the photometric data, we found that it was negligible and excluded it from the total phase curve model. We confidently report the secondary eclipse depth of 494 − 48 + 59 ppm, the most accurate eclipse depth determined so far for WASP-19b, after cleaning the data from the instrumental systematic noise. According to the TESS bandpass, the day and nightside temperatures of WASP-19b are 2245 − 20 + 19 K and 1095 − 21 + 20 , respectively. In addition, we find that the region of maximum brightness is well aligned with the substellar point, implying that there is an inefficient heat distribution from the dayside to the nightside. Our derived A g = 0.11 − 0.03 + 0.03 , suggesting that WASP-19b’s geometric albedo is greater than the geometric albedos of most other hot Jupiters. Finally, the ellipsoidal variation signal amplitude we calculated agrees with theoretical expectations. Our comprehensive model with the approach of Markov Chain Monte Carlo shows the remedy of the degeneracy parameter in photometric data.
Proceedings Of The Institution Of Mechanical Engineers, Part E: Journal Of Process Mechanical Engineering, Feb 16, 2023
Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3... more Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3-TiO2-water, and CuO-TiO2-water nanoparticles in volumetric concentrations of 0.5%, 0.9%, and 2% were studied in a flat tube car radiator. In this work, the thermal performance of hybrid nanofluid will be compared with mono nanofluid and pure water base fluid. These nanoparticles were combined in ratios of (75:25), (50:50), and (25:75) in pure water. Mono and hybrid nanofluids with an inlet temperature of 90 °C, and in different Reynolds numbers (272–816) were studied and numerically simulated. The heat transfer performances of mono and hybrid nanofluids were determined using Nusselt number (Nu), overall heat transfer coefficient ( U), convective heat transfer coefficient ( h), and heat transfer rate ( Qa). The results show an enhancement in the thermal performances of the radiator with an increase in Reynolds number and volume concentration as follows: (Al2O3-water > Al2O3-CuO-water (75:25) > Al2O3-CuO-water (50:50) >Al2O3-CuO-water (25:75) > Al2O3-TiO2-water (75:25) > CuO-TiO2-water (75:25) > Al2O3-TiO2-water (50:50) > CuO-TiO2-water (50:50) > CuO-water > Al2O3-TiO2-water (25:75) > CuO-TiO2-water (25:75) > TiO2-water).
Zenodo (CERN European Organization for Nuclear Research), Jan 27, 2014
In this paper, the effects of gas and liquid superficial inlet velocities and for the first time ... more In this paper, the effects of gas and liquid superficial inlet velocities and for the first time the effect of liquid holdup on slug initiation position are studied experimentally. Empirical correlations are also presented based on the obtained results. The tests are conducted for three liquid holdups in a long horizontal channel with dimensions of 5cmx10cm and 36m length. Usl and Usg rated as to 0.11m/s to 0.56m/s and 1.88m/s to 13m/s, respectively. The obtained results show that as αl=0.25, slug initiation position is increasing monotonically with Usl and Usg. During αl=0.50, slug initiation position is almost constant. For αl=0.75, slug initiation position is decreasing monotonically with Usl and Usg. In the case of equal void fraction of phases, generated slugs are weakly (low pressure). However, for the unequal void fraction of phases strong slugs (high pressure) are formed.
Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering
Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3... more Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3-TiO2-water, and CuO-TiO2-water nanoparticles in volumetric concentrations of 0.5%, 0.9%, and 2% were studied in a flat tube car radiator. In this work, the thermal performance of hybrid nanofluid will be compared with mono nanofluid and pure water base fluid. These nanoparticles were combined in ratios of (75:25), (50:50), and (25:75) in pure water. Mono and hybrid nanofluids with an inlet temperature of 90 °C, and in different Reynolds numbers (272–816) were studied and numerically simulated. The heat transfer performances of mono and hybrid nanofluids were determined using Nusselt number (Nu), overall heat transfer coefficient ( U), convective heat transfer coefficient ( h), and heat transfer rate ( Qa). The results show an enhancement in the thermal performances of the radiator with an increase in Reynolds number and volume concentration as follows: (Al2O3-water > Al2O3-CuO-water ...
We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the ... more We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the short-period transiting hot Jupiter system WASP-19b with a single joint fit to photometric data and resolve parameter degeneracy. We analyze data taken by the Transiting Exoplanet Survey Satellite (TESS) during sectors 9 and 36. We model the data with our five-component model: primary transit, secondary eclipse, ellipsoidal variations, thermal emission, and reflected light, which are jointly fit to extract the information from all parameters simultaneously. The amplitude of Doppler beaming was also estimated to be ∼3 parts-per-million (ppm), but given the precision of the photometric data, we found that it was negligible and excluded it from the total phase curve model. We confidently report the secondary eclipse depth of 494 − 48 + 59 ppm, the most accurate eclipse depth determined so far for WASP-19b, after cleaning the data from the instrumental systematic noise. According to the TESS...
Journal of Mechanical Science and Technology, 2017
In this study, a mathematical model is developed to study Pressure drop oscillations (PDOs) in tw... more In this study, a mathematical model is developed to study Pressure drop oscillations (PDOs) in two horizontal parallel channels using lumped parameter model assuming a homogeneous two-phase flow model. This model investigates the effect of external parameters, such as fluid inertia and compressible gases, on the stability margins of PDOs. Results show that the fluid inertia and compressible gases have high impact on the stability margins of two parallel channels; in fact, increasing the inlet inertia and outlet compressibility increases system stability, while increasing the outlet inertia and inlet compressibility decreases system stability. Thus, increasing the sub-cooling number and inlet resistance coefficient improves stability behavior.
In this research, a theoretical model is presented to investigate the density wave oscillations (... more In this research, a theoretical model is presented to investigate the density wave oscillations (DWOs), in two horizontal parallel channels with lumped parameter model based on two phase homogeneous hypothesis. The parallel channel is composed of the entrance section, heating section and outlet section and the model consists of the boiling channel model, pressure drop model, parallel channel model, constructive model and inertia and compressibility effects, while subcooled boiling effect is neglected and the governing equations are solved by Gear method. The model is validated with experimental data of a single channel flow instability experiment. Then the flow instability in twin channel system is studied under different conditions. This model can analyze the effects of external parameters, such as fluid inertia and compressible gases on the stability margins of density wave oscillations. The results show that, the fluid inertia and compressible gases can significantly change the stability margins of two parallel channels; in fact, the stability behavior of two parallel channel system improves with increasing the inlet inertia and outlet compressibility but, increasing the outlet inertia and inlet compressibility have negative effects the system stability.
يارب دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا : Please cite this article using: M. R. Ansar... more يارب دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا : Please cite this article using: M. R. Ansari, E. Salimi, B. Habibpour, P. Adibi, Numerical simulation and investigation of bubble velocity and deformation in inclined channel with two consecutive slopes using VOF-PLIC method, Modares Mechanical Engineering, Vol. 14, No. 11, pp. 29-36, 2014 (In Persian) هیبش بیش لاناک رد بابح لکش رییغت و تعرس یسررب و يددع يزاس بیش ود اب راد
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Dec 6, 2021
The flow around a circular-cone is 3D, unsteady and turbulent. As reported in many research works... more The flow around a circular-cone is 3D, unsteady and turbulent. As reported in many research works on this type of flow, boundary layer separations, vortex structures and the effect of surface roughness are strongly related. The effect of roughness is still not completely understood and proves challenging both for numerical and experimental approaches. The present work aims to gain more insights in understanding and numerically predicting this type of flows. Particularly, it attempts to improve the accuracy of numerical predictions of the effects of roughness on the asymmetric vortex flow around a circular-cone at subsonic flow conditions. This is performed using numerical simulations, which predict the flow field details across different transversal stations along the cone. Therefore, we have analyzed the effect of many turbulence models, notably, the transition SST, using ANSYS Fluent code. Flows characteristics are highlighted and validated against the well-known theory and some experimental measurements. The findings depict that a surface roughness height about 0.32 mm has efficaciously triggered the boundary layer to change from a laminar to a fully turbulent state in both sides of the body, in addition to a significant reduction in the global lateral force. Moreover, it seems that the roughness reduces the asymmetry of the vortex in the leeward side of the cone. Testing many roughness heights has allowed us to determine the way in which it is possible to reduce the side force effectively at high angles of attack without affecting the lift of the cone cylinder.
We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the ... more We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the short-period transiting hot Jupiter system WASP-19b with a single joint fit to photometric data and resolve parameter degeneracy. We analyze data taken by the Transiting Exoplanet Survey Satellite (TESS) during sectors 9 and 36. We model the data with our five-component model: primary transit, secondary eclipse, ellipsoidal variations, thermal emission, and reflected light, which are jointly fit to extract the information from all parameters simultaneously. The amplitude of Doppler beaming was also estimated to be ∼3 parts-per-million (ppm), but given the precision of the photometric data, we found that it was negligible and excluded it from the total phase curve model. We confidently report the secondary eclipse depth of 494 − 48 + 59 ppm, the most accurate eclipse depth determined so far for WASP-19b, after cleaning the data from the instrumental systematic noise. According to the TESS bandpass, the day and nightside temperatures of WASP-19b are 2245 − 20 + 19 K and 1095 − 21 + 20 , respectively. In addition, we find that the region of maximum brightness is well aligned with the substellar point, implying that there is an inefficient heat distribution from the dayside to the nightside. Our derived A g = 0.11 − 0.03 + 0.03 , suggesting that WASP-19b’s geometric albedo is greater than the geometric albedos of most other hot Jupiters. Finally, the ellipsoidal variation signal amplitude we calculated agrees with theoretical expectations. Our comprehensive model with the approach of Markov Chain Monte Carlo shows the remedy of the degeneracy parameter in photometric data.
Proceedings Of The Institution Of Mechanical Engineers, Part E: Journal Of Process Mechanical Engineering, Feb 16, 2023
Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3... more Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3-TiO2-water, and CuO-TiO2-water nanoparticles in volumetric concentrations of 0.5%, 0.9%, and 2% were studied in a flat tube car radiator. In this work, the thermal performance of hybrid nanofluid will be compared with mono nanofluid and pure water base fluid. These nanoparticles were combined in ratios of (75:25), (50:50), and (25:75) in pure water. Mono and hybrid nanofluids with an inlet temperature of 90 °C, and in different Reynolds numbers (272–816) were studied and numerically simulated. The heat transfer performances of mono and hybrid nanofluids were determined using Nusselt number (Nu), overall heat transfer coefficient ( U), convective heat transfer coefficient ( h), and heat transfer rate ( Qa). The results show an enhancement in the thermal performances of the radiator with an increase in Reynolds number and volume concentration as follows: (Al2O3-water > Al2O3-CuO-water (75:25) > Al2O3-CuO-water (50:50) >Al2O3-CuO-water (25:75) > Al2O3-TiO2-water (75:25) > CuO-TiO2-water (75:25) > Al2O3-TiO2-water (50:50) > CuO-TiO2-water (50:50) > CuO-water > Al2O3-TiO2-water (25:75) > CuO-TiO2-water (25:75) > TiO2-water).
Zenodo (CERN European Organization for Nuclear Research), Jan 27, 2014
In this paper, the effects of gas and liquid superficial inlet velocities and for the first time ... more In this paper, the effects of gas and liquid superficial inlet velocities and for the first time the effect of liquid holdup on slug initiation position are studied experimentally. Empirical correlations are also presented based on the obtained results. The tests are conducted for three liquid holdups in a long horizontal channel with dimensions of 5cmx10cm and 36m length. Usl and Usg rated as to 0.11m/s to 0.56m/s and 1.88m/s to 13m/s, respectively. The obtained results show that as αl=0.25, slug initiation position is increasing monotonically with Usl and Usg. During αl=0.50, slug initiation position is almost constant. For αl=0.75, slug initiation position is decreasing monotonically with Usl and Usg. In the case of equal void fraction of phases, generated slugs are weakly (low pressure). However, for the unequal void fraction of phases strong slugs (high pressure) are formed.
Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering
Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3... more Forced heat transfer of Al2O3-water, CuO-water, and TiO2-water nanofluids, Al2O3-CuO-water, Al2O3-TiO2-water, and CuO-TiO2-water nanoparticles in volumetric concentrations of 0.5%, 0.9%, and 2% were studied in a flat tube car radiator. In this work, the thermal performance of hybrid nanofluid will be compared with mono nanofluid and pure water base fluid. These nanoparticles were combined in ratios of (75:25), (50:50), and (25:75) in pure water. Mono and hybrid nanofluids with an inlet temperature of 90 °C, and in different Reynolds numbers (272–816) were studied and numerically simulated. The heat transfer performances of mono and hybrid nanofluids were determined using Nusselt number (Nu), overall heat transfer coefficient ( U), convective heat transfer coefficient ( h), and heat transfer rate ( Qa). The results show an enhancement in the thermal performances of the radiator with an increase in Reynolds number and volume concentration as follows: (Al2O3-water > Al2O3-CuO-water ...
We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the ... more We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the short-period transiting hot Jupiter system WASP-19b with a single joint fit to photometric data and resolve parameter degeneracy. We analyze data taken by the Transiting Exoplanet Survey Satellite (TESS) during sectors 9 and 36. We model the data with our five-component model: primary transit, secondary eclipse, ellipsoidal variations, thermal emission, and reflected light, which are jointly fit to extract the information from all parameters simultaneously. The amplitude of Doppler beaming was also estimated to be ∼3 parts-per-million (ppm), but given the precision of the photometric data, we found that it was negligible and excluded it from the total phase curve model. We confidently report the secondary eclipse depth of 494 − 48 + 59 ppm, the most accurate eclipse depth determined so far for WASP-19b, after cleaning the data from the instrumental systematic noise. According to the TESS...
Journal of Mechanical Science and Technology, 2017
In this study, a mathematical model is developed to study Pressure drop oscillations (PDOs) in tw... more In this study, a mathematical model is developed to study Pressure drop oscillations (PDOs) in two horizontal parallel channels using lumped parameter model assuming a homogeneous two-phase flow model. This model investigates the effect of external parameters, such as fluid inertia and compressible gases, on the stability margins of PDOs. Results show that the fluid inertia and compressible gases have high impact on the stability margins of two parallel channels; in fact, increasing the inlet inertia and outlet compressibility increases system stability, while increasing the outlet inertia and inlet compressibility decreases system stability. Thus, increasing the sub-cooling number and inlet resistance coefficient improves stability behavior.
In this research, a theoretical model is presented to investigate the density wave oscillations (... more In this research, a theoretical model is presented to investigate the density wave oscillations (DWOs), in two horizontal parallel channels with lumped parameter model based on two phase homogeneous hypothesis. The parallel channel is composed of the entrance section, heating section and outlet section and the model consists of the boiling channel model, pressure drop model, parallel channel model, constructive model and inertia and compressibility effects, while subcooled boiling effect is neglected and the governing equations are solved by Gear method. The model is validated with experimental data of a single channel flow instability experiment. Then the flow instability in twin channel system is studied under different conditions. This model can analyze the effects of external parameters, such as fluid inertia and compressible gases on the stability margins of density wave oscillations. The results show that, the fluid inertia and compressible gases can significantly change the stability margins of two parallel channels; in fact, the stability behavior of two parallel channel system improves with increasing the inlet inertia and outlet compressibility but, increasing the outlet inertia and inlet compressibility have negative effects the system stability.
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