China
Africa
Explore chapters and articles related to this topic
Transpiration Cooling Using Porous Material for Hypersonic Applications
Published in Yasser Mahmoudi, Kamel Hooman, Kambiz Vafai, Convective Heat Transfer in Porous Media, 2019
Adriano Cerminara, Ralf Deiterding, Neil D. Sandham
On the surface of a slender body, in contrast, the aerodynamic heating is caused by the dissipation of a large amount of kinetic energy (related to the high streamwise speed u at the boundary-layer edge) inside the boundary layer due to viscosity. This represents the main mechanism acting on the surface section downstream of the vehicle leading edge. As a consequence of the viscous effects, the temperature increases continually with reducing velocity as the wall is approached, until it reaches a peak at a certain distance from the surface, and then rapidly decreases to the fixed (low) value at the wall (Tw). As the temperature peak is located near the wall, this results in a steep gradient on the vehicle surface, that is, a high heat flux. This is a peculiar feature of high-speed boundary layers, as compared to low-speed (subsonic) cases, which is due to the fact that in the high-speed case, the contribution of the kinetic-energy dissipation in the energy balance within the boundary layer is no longer negligible.
Hypersonic Aircraft
Published in G. Daniel Brewer, Hydrogen Aircraft Technology, 2017
Aerodynamic heating is a function of the heat transfer coefficient and the recovery or adiabatic wall temperature. With transition based on a local Reynolds number of 1 million, for the subject configuration at the specified flight Mach number and altitude, turbulent flow exists over all surfaces except for the first foot or so of the fuselage nose and the wing leading edges. For the 7° cruise angle of attack, external heat transfer coefficients are higher for the lower surface than for the upper surface because of higher local pressures on the lower surfaces due to flow compression. Conversely, on the upper surfaces, flow expansion reduces local pressures below freestream ambient, with an attendant reduction in the heat transfer coefficients. This, of course, accounts for the differences in skin temperatures between the upper and lower surfaces. The temperatures shown on Figure 5–20 account for relief due to radiation from the surfaces. This temperature relief is significant at speeds above Mach 2.
Characteristics of Polymers and Polymerization Processes
Published in Manas Chanda, Plastics Technology Handbook, 2017
Most notable applications of ablative materials are in protecting space vehicles during reentry into the earth's atmosphere, protecting missile nose cones subjected to aerodynamic heating during hypersonic fight in the atmosphere, insulating sections of rocket motors from hot propulsion gases, resisting the intense radiant hear of thermonuclear blasts, and providing thermal protection for structural materials exposed to very high temperatures.
Aerothermodynamic design and performance analysis of modified nose cones for space reentry vehicles
Published in International Journal of Ambient Energy, 2022
Raja Muthu, S. Siva Lakshmi, Santhoshini Babu
The fundamental basis for the design of any hypersonic vehicle is the analysis of aerodynamic and aerothermodynamic characteristics. Reentry vehicle is a portion of a spacecraft that is designed mainly to protect the crew and instruments within it during its return through Earth's atmosphere. It has to sustain intense heating effects caused during the high-speed flight through the atmosphere. The successful reentry of space vehicles is only become possible after the selection of the optimum design concept by considering aerodynamic heating, air loads and aerodynamic drag (Hankey 1988). The nose cone shape of any flying vehicles is important because it experiences the maximum amount of heat loads. There are many nose cone shapes used such as blunt-cone, hemisphere, ogive, parabola, spherical, etc. (Anderson 2008). Due to the high-speed passage of air around the reentry vehicles during its return, aerodynamic heating occurs whereby its kinetic energy is transformed into heat energy by skin friction on the surface of the body at a rate that depends on the viscosity and speed of the air. Aerodynamic heating can completely disintegrate even smaller objects and may cause objects to explode. When an entry body penetrates the atmosphere, the reentry velocities are extremely high and the corresponding Mach numbers are very huge (hypersonic velocities) (Harish, Naveen, and Rajgopal 2014). With the advent of hypersonic entry vehicles in the space age, aerodynamic heating became an overriding problem with regard to the very survival of the vehicle itself. It even dictates the shape of the vehicle. The shape of the nose cone is very important because when compared with all parts of the reentry vehicle, only the nosecone region experiences more heating loads (Anderson 2008).
Effect of Thermal Ablation at the Fluid-Solid Interface of a Hypersonic Reentry Vehicle in Rarefied Flow Regime
Published in International Journal of Computational Fluid Dynamics, 2021
A HYPERSONIC atmospheric reentry vehicle (ARV) endures an extreme aerothermodynamic environment as its enormous kinetic energy gets transformed into thermal energy. As a consequence of aerodynamic heating, a vehicle experiences high heat loads while decelerating towards a planet surface. While descending, a space vehicle goes through a range of altitudes that extends from free molecular to continuum through a transitional regime with a Knudsen number varying from more than 10 to less than 0.01. The heat flux can reach a maximum value when the vehicle cruises at hypersonic velocity and the flow field exists in a semi-rarefied regime. High-temperature gases surrounding a reentry vehicle are in a thermal and chemical non-equilibrium state in these conditions. In the transitional regime, flow is neither continuum nor free molecular and the conventional Navier-Stokes equation cannot accurately predict the flow physics in such conditions, as the continuum assumption breaks down, requiring the use of the Boltzmann equation as the governing equation. Although the Boltzmann equation governs the flow in all regimes, obtaining a numerical solution is still challenging. In order to predict the fluid flow behaviour in such transitional regimes, Direct Simulation Monte Carlo (DSMC) method was proposed by G.A. Bird to solve rarefied flows using dilute gas assumption (Bird 1994). The particle-based DSMC method is a pure simulation approach that is employed to approximate the solution of the Boltzmann equation numerically. DSMC method deals with simulated particles each of which represents a large number of real molecules. Its results have been proven to converge toward the solutions of the Boltzmann equation in the limit of an infinite number of simulated particles, with cell size smaller than the mean free path and a time step smaller than the mean collision time (Bird 1970; Nanbu 1986).