Papers by Antonio Viviani
Aerotecnica Missili & Spazio, 2017
The paper deals with the aerodynamic performance analysis of three reusable and unmanned flying l... more The paper deals with the aerodynamic performance analysis of three reusable and unmanned flying laboratories designed to perform a return flight from low Earth orbit to provide experimental data in the framework of re-entry technologies. Several design approaches, ranging from low-order methods to computational fluid dynamics analyses, have been addressed in this work. In particular, vehicles aerodynamic performances for a wide range of free stream flow conditions, from subsonic to hypersonic regime, including reacting and non-reacting flow and different angles of attack have been provided and in some cases compared. Computational fluid dynamics results confirm that real gas effects seem to be fundamental for the assessment of the concept aerodynamics, especially concerning pitching moment evaluation.
European Journal of Mechanics B-fluids, Nov 1, 2020
The longwave oscillatory Marangoni convection in a horizontal two-layer film heated from above, i... more The longwave oscillatory Marangoni convection in a horizontal two-layer film heated from above, in the presence of an interfacial heat consumption, is considered. The effect of gravity is taken into account. The action of a time-periodic parameter modulation on the nonlinear Marangoni waves is investigated. The problem is studied numerically in the framework of longwave amplitude equations. The alternating rolls patterns and the oscillating squares have been found. In some intervals of the modulation frequency the phenomenon of synchronization has been observed.
Microgravity Science and Technology, 1997
info:eu-repo/semantics/publishe
International Journal of Thermal Sciences, Sep 1, 2017
Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effect... more Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effects in a two-layer system with rigid heat-insulated lateral walls, have been investigated. The influence of a temperature-dependent interfacial heat release/consumption on oscillatory regimes under the action of an inclined temperature gradient, has been studied. It is shown that sufficiently strong temperature dependence of interfacial heat sources and heat sinks can lead to the change of the sequence of bifurcations and the development of new nonlinear regimes. Specifically, the period doubling bifurcations have been obtained.
Comptes Rendus Mecanique, Mar 1, 2008
The nonlinear buoyant-thermocapillary flows in a three-layer system, filling a closed cavity and ... more The nonlinear buoyant-thermocapillary flows in a three-layer system, filling a closed cavity and subjected to a temperature gradient directed along the interfaces, are investigated. The nonlinear simulations of convective regimes are performed by the finite-difference method. It is found that for sufficiently large values of the Grashof number, the long vortices turn into multicell structures. To cite this article: I.
Proceedings of the International Astronautical Congress, IAC, 2012
The influence of the horizontal component of the temperature gradient on nonlinear oscillatory co... more The influence of the horizontal component of the temperature gradient on nonlinear oscillatory convective flows, developed under the joint action of buoyant and thermocapillary effects in the 47 v2 silicone oil - water system, is investigated. The layers with different thicknesses are considered. Transitions between nonlinear regimes of convection, have been studied. It is shown that under the action of the horizontal component of the temperature gradient, the asymmetric oscillatory flow takes place in the system. ©(2012) by the International Astronautieal Federation.
Microgravity Science and Technology, Aug 19, 2008
The concentration convection in an isothermal liquid near a drop (or an air bubble) clamped betwe... more The concentration convection in an isothermal liquid near a drop (or an air bubble) clamped between the vertical walls of a horizontal channel is studied numerically within the framework of two simple mathematical models: with and without the surface phase at the drop–liquid interface formed by adsorption/desorption process. The interaction between the buoyancy and the Marangoni convective flows is responsible
Microgravity Science and Technology, Jun 3, 2011
The influence of the horizontal component of the temperature gradient on nonlinear regimes of osc... more The influence of the horizontal component of the temperature gradient on nonlinear regimes of oscillatory convection developed under the joint action of buoyant and thermocapillary effects in a multilayer system, is investigated. The nonlinear two-dimensional convective regimes are studied by the finite difference method. The interfaces are assumed to be nondeforming. The rigid heat-insulated lateral walls are considered. Transitions between different oscillatory and steady flow regimes have been studied. Specifically, it is shown that the horizontal component of the temperature gradient leads to the violation of the symmetry conditions and the appearance of the asymmetric oscillatory flows. The cavities with different lengths have been considered.
Physics of Fluids, 2011
The nonlinear development of oscillatory instability under the joint action of buoyant and thermo... more The nonlinear development of oscillatory instability under the joint action of buoyant and thermocapillary effects in multilayer system is investigated. The nonlinear convective regimes are studied by the finite difference method. The calculations have been performed for two-dimensional flows. The interfaces are assumed to be nondeforming. Rigid heat-insulated lateral walls are considered. Transitions between the flows with different spatial structures are studied. Specific types of nonlinear flows-symmetric and asymmetric oscillations-have been found. It is shown that the oscillatory flow takes place in an interval of Grashof number values bounded both from below by the quiescent mechanical equilibrium, and from above by a convecting steady state. Cavities with different lengths are considered.
Microgravity Science and Technology, Feb 8, 2016
Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effect... more Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effects in a two-layer system with periodic boundary conditions on the lateral walls, have been investigated. The influence of a temperature-dependent interfacial heat release/consumption on oscillatory regimes, has been studied. It is shown that sufficiently strong temperature dependence of interfacial heat sources and heat sinks can lead to the change of the sequence of bifurcations and the development of new nonlinear regimes.
Physics of Fluids, Oct 1, 2012
The influence of the horizontal component of the temperature gradient on nonlinear regimes of osc... more The influence of the horizontal component of the temperature gradient on nonlinear regimes of oscillatory convection developed under the joint action of buoyant and thermocapillary effects in a multilayer system, is investigated. The nonlinear two-dimensional convective regimes are studied by the finite difference method. The interfaces are assumed to be nondeforming. The rigid heat-insulated lateral walls are considered. Transitions between different oscillatory and steady flow regimes have been studied. Specifically, it is shown that the horizontal component of the temperature gradient leads to the violation of the symmetry conditions and the appearance of the asymmetric oscillatory flows. The cavities with different lengths have been considered.
Acta Astronautica, Jun 1, 2018
convective flows in a twolayer system under the action of spatial temperature modulation of heat ... more convective flows in a twolayer system under the action of spatial temperature modulation of heat release/consumption at the interface,
Acta Astronautica, Jun 1, 2016
The influence of an interfacial heat release and heat consumption on nonlinear convective flows, ... more The influence of an interfacial heat release and heat consumption on nonlinear convective flows, developed under the joint action of buoyant and thermocapillary effects in a laterally heated two-layer system with periodic boundary conditions, is investigated. Regimes of traveling waves and modulated traveling waves have been obtained. It is found that rather intensive heat sinks at the interface can lead to the change of the direction of the waves' propagation.
European Journal of Mechanics B-fluids, Mar 1, 2018
Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effect... more Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effects in a two-layer system with rigid heat-insulated lateral walls, have been investigated. The influence of a temperature-dependent interfacial heat release/consumption on oscillatory regimes, has been studied. It is shown that sufficiently strong temperature dependence of interfacial heat sources and heat sinks can lead to the change of the sequence of bifurcations and the development of new nonlinear regimes. Specifically, the period doubling bifurcations have been found.
International Journal of Thermal Sciences, Mar 1, 2017
The influence of an interfacial heat release on nonlinear convective regimes, developed under the... more The influence of an interfacial heat release on nonlinear convective regimes, developed under the action of an imposed temperature gradient in the 47v2 silicone oil-water system, has been studied. Rigid heatinsulated lateral walls, corresponding to the case of closed cavities, have been considered. Transitions between the flows with different spatial structures, have been investigated. It is shown that the presence of an interfacial heat release can change the sequence of bifurcations and lead to the appearance of specific oscillatory regimes.
Microgravity Science and Technology, Jan 24, 2018
Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effect... more Nonlinear convective flows developed under the joint action of buoyant and thermocapillary effects in a laterally heated two-layer system filling the closed cavity, have been investigated. The influence of a temperature-dependent interfacial heat release/consumption on nonlinear steady and oscillatory regimes, has been studied. It is shown that sufficiently strong temperature dependence of interfacial heat sinks and heat sources can change the sequence of bifurcations and lead to the development of specific oscillatory regimes in the system.
Energies
A numerical procedure was developed to determine a variable-pitch law that maximized the performa... more A numerical procedure was developed to determine a variable-pitch law that maximized the performance of a vertical-axis wind turbine (VAWT). The methodology was based on the determination, for each blade, of the angle of attack maximizing the stationary aerodynamic efficiency at prescribed azimuthal positions. The angles of attack were determined by means of a panel method with a low computational effort, and the methodology was implemented in Matlab® software (version R2021a) allowing us to achieve in real time a variable-pitch law suitable for the turbine geometry. The variable pitch law was validated by considering its effect on the torque of a 2D model of an H-Darrieus turbine. U-RANS analyses were carried out with a K−ωSST model and a sliding-mesh technique was used to prescribe the blade motion around the shaft and pitch motion. Results showed how the variable-pitch law delayed the dynamic stall and improved the aerodynamic performance considerably.
Hypersonic Vehicles - Applications, Recent Advances, and Perspectives [Working Title], 2022
In the present work, a feasibility study of a manned Mars entry, descent, and landing mission, pe... more In the present work, a feasibility study of a manned Mars entry, descent, and landing mission, performed with a lifting vehicle, is analyzed. Mars entry challenges relate to different atmosphere models; consequently, the effective landing capability of a winged configuration is discussed. An entry trajectory study in the Martian atmosphere assuming both a planar and non-planar three degree-of-freedom model is performed. Peak heat rates and time-integrated heat loads during the descent are computed verifying the entry corridor. It is shown that prescribed aerodynamic performances can be modulated explicitly by varying angle of attack and implicitly with bank-angle modulation. Finally, the resulting trajectory is discussed in terms of g-loads, total range performances, and integral heat load absorbed, in the perspective of future manned exploration missions.
Uploads
Papers by Antonio Viviani