Influence of vibrational relaxation on perturbations in a shock layer on a plate

AIP Conference Proceedings

Mironov

et al. 2017

Self Cite

Abstract. Within the framework of the skeleton model of a porous medium, numerical simulation of two tasks was performed: task of the absorption of acoustic disturbances at hypersonic flow past a plate with a porous insert taking into account the real properties of the gas and task of a supersonic flow around a streamwise aligned cylinder with a frontal insert from cellular porous nickel. It is shown that high porous cellular materials can effectively be used in supersonic aerodynamics.

Section: Methods Of Sound-absorbing Coatings In Vibrationally Excited mentioning

confidence: 99%

Numerical simulation of highly porous materials in application to supersonic aerodynamics

AIP Conference Proceedings

Mironov

et al. 2017

Self Cite

“…Nowadays large scientific experience has been accumulated in studying the effect of physical and chemical processes in gases on the mean flow around bodies at hypersonic velocities [1]. However, there are only a few papers on stability of such flows (e.g., [2][3][4]). …”

Section: Introductionmentioning

confidence: 99%

“…The present research is focused on experiments conducted in the IT-302M hot-shot wind tunnel based at ITAM SB RAS [4] where the characteristics of the mean flow and pressure fluctuations on the surface of a solid plate and a plate with a porous insert made of foamed nickel (a porosity coefficient of 95%) were measured in mixtures of air and CO2. The rectangular sound-absorbing insert was located on a plate of length L = 200 mm, width of 50 mm, and thickness of 25 mm at a distance of 90mm from the leading edge.…”

Section: Introductionmentioning

confidence: 99%

“…It is shown [7] that the method of sound-absorbing coatings is also effective in hypersonic flows of vibrationally excited carbon dioxide. However, the intensity of relaxation processes and their influence on the evolution of disturbances in a mixture with other gases can differ from the processes in pure CO2.The present research is focused on experiments conducted in the IT-302M hot-shot wind tunnel based at ITAM SB RAS [4] where the characteristics of the mean flow and pressure fluctuations on the surface of a solid plate and a plate with a porous insert made of foamed nickel (a porosity coefficient of 95%) were measured in mixtures of air and CO2. The rectangular sound-absorbing insert was…”

mentioning

confidence: 99%

See 1 more Smart Citation

Effect of sound-absorbing coatings on the disturbance evolution in a flow of a mixture of vibrationally excited gases

Reshetova

et al. 2017

J. Phys.: Conf. Ser.

Abstract. The flow around a solid plate and a plate with a sound-absorbing coating at a nonzero angle of attack in a hypersonic flow (М=8.44) of a mixture of vibrationally excited carbon dioxide and nitrogen is considered. Numerical simulations are performed by solving twodimensional unsteady Navier-Stokes equations with a two-temperature model of relaxing flows. The vibrational energy as a function of time is defined by the Landau−Teller equation. A skeleton model, which is a set of square elements arranged in a staggered order, is used for simulating the porous coating made of foamed nickel with a porosity coefficient of 95%. The distance between the elements is equal to the pore diameter of the real sound-absorbing material. Data on the evolution of disturbances on the solid plate and on the plate with the soundabsorbing coating are presented for various angles of attack and CO2 concentrations in the mixture. The experimental and calculated data on pressure fluctuations on the plate surfaces are found to be in good agreement. The effects of various parameters of the sound-absorbing coating (depth, length, and location at the flat plate) are considered. It is shown that the soundabsorbing coating significantly reduces the intensity of pressure fluctuations on the plate surface as compared to the solid surface (up to 50% depending on the length and location of the sound-absorbing coating). IntroductionThe possibility of controlling the intensity of disturbances in boundary layers and the transition to turbulence is one of the important aspects of the development of perspective hypersonic aircraft. Real gas effects associated with excitation of vibrational degrees of freedom of molecules and flow nonequilibrium are manifested under real flight conditions, where high speeds and temperatures are observed. Real gas properties can significantly affect the generation and evolution of disturbances in the boundary layer and, as a consequence, the transition to turbulence. Nowadays large scientific experience has been accumulated in studying the effect of physical and chemical processes in gases on the mean flow around bodies at hypersonic velocities [1]. However, there are only a few papers on stability of such flows (e.g., [2][3][4]).Disturbances formed in the shock layer are carried downstream and affect the evolution of disturbances and the laminar-turbulent transition in the hypersonic boundary layer on a model. One of the known methods for controlling the laminar-turbulent transition in moderately hypersonic flows is the method of applying a sound-absorbing coating onto the surface [5]. The method of sound-absorbing coatings has proved its effectiveness for low-temperature flows at М=21 [6]. It is shown [7] that the method of sound-absorbing coatings is also effective in hypersonic flows of vibrationally excited carbon dioxide. However, the intensity of relaxation processes and their influence on the evolution of disturbances in a mixture with other gases can differ from the processes in pure CO2.The present res...

“…These phenomena are based on dissipation of the energy of acoustic disturbances, which are a dominating mode of instability of a hypersonic boundary layer, owing to friction in pores of the coating. It was shown in experiments [6] that the intensity of perturbations is attenuated by a sound-absorbing coating from the HPCM by 20% at the plate in the flow of vibrationally excited mixtures of CO 2 with air.To increase the efficiency of the action of gas-permeable porous materials on a supersonic flow around various bodies and develop engineering methods for design of supersonic flying vehicles with porous control elements it is required to apply modern methods of numerical simulation of flow around bodies with porous inserts. At present, the main problem of numerical modeling is the optimal choice of the model of a gas permeable porous medium.…”

mentioning

confidence: 99%

Simulation of a supersonic flow around a body with a frontal gas-permeable insert by using a skeleton model of a highly porous cellular material

Mironov

2017

J. Phys.: Conf. Ser.

Abstract. Numerical simulation of supersonic flow past a cylinder with a frontal gas-permeable insert is performed using the skeleton model of a highly porous cellular material. Numerical simulation was carried out within the framework of two-dimensional RANS equations written in an axisymmetric form. The skeleton model is a system of coaxial rings of different diameters, arranged in staggered order. The calculations were carried out in a wide range of determining parameters: Mach numbers M ∞ =3, 4.85 and 7, unit Reynolds numbers Re 1 =13.8×10 5 ÷ 13.8×10 6 m -1 , the cylinder diameter 6÷40mm, the length of the porous insert 3÷45mm, the cell diameter of 1 and 3 mm. The results of the calculations are consistent with the available experimental data. The applicability of the skeleton model for the description of supersonic flow around axisymmetric bodies with front inserts from cellular-porous materials is shown. IntroductionGas-permeable porous materials in recent years have found application in promising methods of controlling supersonic aircraft [1][2][3]. Experimental studies in wind tunnels demonstrated the possibility of controlling supersonic flow and, in particular, controlling the aerodynamic drag of bodies by help of gas permeable highly porous cellular materials (HPCM) [1,4].HPCM ( Figure 1a) is formed when the foamed liquid metals solidify. The cellulars of the frozen foam form a spatial carcass from the partitions between the contacting cellulars. The porosity (the ratio of the total volume of the porous sample to the volume of the skeleton) of such a material lies in the range from 76% to 98%. The material ceases to be gas permeable with less porosity, and with greater porosity, a skeleton of the partitions is not formed. There are some recent applications of gas-permeable porous materials and in supersonic aerodynamics to suppress acoustic waves. In particular, it was possible to suppress acoustic disturbances in the shock layer on a plate in nitrogen stream at M = 21 with the help of inserts of foamed nickel in experiments [5]. These phenomena are based on dissipation of the energy of acoustic disturbances, which are a dominating mode of instability of a hypersonic boundary layer, owing to friction in pores of the coating. It was shown in experiments [6] that the intensity of perturbations is attenuated by a sound-absorbing coating from the HPCM by 20% at the plate in the flow of vibrationally excited mixtures of CO 2 with air.To increase the efficiency of the action of gas-permeable porous materials on a supersonic flow around various bodies and develop engineering methods for design of supersonic flying vehicles with porous control elements it is required to apply modern methods of numerical simulation of flow around bodies with porous inserts. At present, the main problem of numerical modeling is the optimal choice of the model of a gas permeable porous medium. Continuum models of a porous medium with a prescribed pressure gradient in the porous region as a function of the filtration rate in ac...