Fluid Thermal Interaction Research Articles

Numerical investigation on the performance of combinational spike and transpiration cooling concept for nose cone under hypersonic conditions

Abstract Aiming at solving the thermal protection problems of the nose cone for hypersonic vehicles, a novel combinational spike and transpiration cooling concept is proposed in this paper. Although the temperature of the nose cone structure can be effectively reduced by traditional transpiration cooling, the cooling effect is not ideal due to the extremely high heat flux and pressure near the stagnation point. In the combinational configuration, the bow shock wave at the leading edge of the nose cone is pushed away by the spike, so that the pressure and heat flux along the nose cone surface are reduced obviously, and the cooling effect is also improved significantly. The flow field generated by this innovative concept has been thoroughly examined through numerical simulations employing the compressible Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with the shear stress transport (SST) k-ω turbulence model. The fluid-thermal interaction is considered by using the conjugate heat transfer approach. The performance of three configurations based on the nose cone are numerically investigated, including transpiration cooling, spike, combinational spike and transpiration cooling. The numerical results show that, compared with the traditional transpiration cooling, the temperature at the stagnation point of the nose cone for the combinational configuration is reduced by about 64%, which proves the feasibility and high efficiency of the novel combinational concept. With the increase of coolant mass flow, the temperature along the nose cone surface for combinational configuration decreases, while the magnitude of the temperature reduction decreases. Therefore, under certain incoming flow conditions, the appropriate coolant mass flow should be considered to achieve better thermal protection effect.

Flow-thermal coupled investigation on hypersonic spike-jet with channel

As for blunt-body hypersonic vehicles, the extreme drag and aero-heating pose great challenges to the conceptual design. Different from the conventional configurations, a blunt body slotted with a channel is proposed in this paper. The channel is further combined with a jet on the shoulder to reduce drag and aero-heating. Simultaneously, based on the position of the separation point and vortex edge, a modified effective body approach is developed to accurately investigate the drag reduction mechanism. Specifically, the more slender the modified effective body is, the more obvious the drag reduction is. The simulation results show that the spike-channel-jet can push the shear layer on the spike away from the wall. In this way, the position of shear reattachment point moves downstream, which can enlarge the recirculation zone and weaken the shock-shock interaction. Additionally, the reattachment shock is pushed far away from the blunt body, which is also weakened. For drag, net power is introduced to evaluate the practical value of spike-channel-jet for drag reduction. Compared with a simple spike (spike length L/D = 1) of the same size, the spike-channel-jet can reduce the total drag by 24.68 %, the peak pressure coefficient of the blunt body by 38.54 %, the peak temperature of the blunt body by 65.75 %, and the peak temperature of the spike by 10.63 %. The maximum net power can reach 13.30 kW. Considering the fluid-thermal interaction, the findings reveal the influence of the spike length and jet mass flow rate on aerodynamic performance, by modified effective body further analyze the drag reduction mechanism with the jet, and validate the different reasons for the peak temperature and pressure of the blunt body.

Coupled investigation on drag and heat flux reduction over spiked waverider with a wide-speed range

When flying at supersonic/hypersonic speeds, the vehicles constantly suffer from extremely complex aerodynamic and aerothermodynamic environment. In order to investigate the drag reduction and thermal protection characteristics of hypersonic vehicles, the spike, as well as the combined spike and opposing jet strategy, are applied to the waverider. The effects of different strategies and angle of attack on the flow field structure and the aerodynamic characteristics of a waverider are studied, and the fluid-thermal interaction between the three-dimensional flow field and the internal structure is explored. The angle of attack has significant influences on the lift and drag coefficient values, and increasing the angle of attack can further increase the lift and drag coefficient values, but result in the decrease of the lift-to-drag ratio. The coupled analysis results indicate that a prominent reduction in the drag and aeroheating is achieved when the combined spike and opposing jet strategy is added to the waverider, and the flow field structure changes remarkably during the coupling process.

Heat transfer with interface effects in high-enthalpy and high-speed flow: Modelling review and recent progress

Aerodynamics, aerothermodynamics and thermal protection system response in high-enthalpy and high-speed flow is heat transfer with interface effects in nature. Modelling and simulation of these phenomena are of vital significance to ensure high-speed flight thermal safety. The heat transfer phenomena related with gas-surface interaction, interface heterogeneous reactions and microstructure morphology in high-enthalpy and high-speed flow were summarized. The modelling of interface effects and the corresponding coupling algorithms for computational fluid dynamics (CFD) and related approaches were reviewed. Recent research activities for interface problems in high-enthalpy and high-speed flow at China Aerodynamics Research and Development Center were discussed. They mainly focus on practical solutions of computational fluid dynamics with viscous wall boundary conditions, multi-zone coupling for fluid-thermal interaction and cross-scale algorithms of CFD coupled with smaller scale theoretical approaches. Finally, further perspectives about heat transfer with interface effects were proposed, including mesoscale experimental verification, interface cross-scale modelling and accuracy/uncertainty of coupling algorithms.

Aeroheating reduction for blunt body using aerodome jet

A novel thermal protection concept that combines the aerodome and cooling nitrogen is introduced for aeroheating reduction in high-speed flights. Study involves the fluid–thermal interaction between the blunt body and surrounding fluid. After detailed grid and time step verification and numerical validation with available experimental results, the influence of jet pressure and jet distance on the aeroheating reduction performance are analyzed comprehensively. Results indicate that the advantages of the novel combination of aerodome and cooling nitrogen over the conventional opposing jet are mainly embodied in the following three aspects. Firstly, the stability of both the aerodome-jet and the flow field structure can be ensured in wide ranges of flight speed and jet pressure, due to the existence of aerodome. Secondly, on the premise of providing overall thermal protection for the blunt body, emphasis is placed on the direct and continuous cooling of the front part of blunt body where severe aeroheating occurs. Thirdly, the thermal protection performance can be improved without sacrificing the drag reduction performance by selecting a suitable set of jet pressure and jet distance.

Numerical evaluation of aerodome and cooling jet for aeroheating reduction

Thermal protection is one of the major challenges faced by engineers when designing hypersonic vehicles. Mounting a spike ahead of a vehicle's blunt nose provides at least a partial solution for the longtime aeroheating caused by high-speed flow; however, this solution appears inadequate at high Mach numbers. This study presents three innovative solutions, namely, the double-aerodome concept, the introduction of a cooling jet on the aerodome and the combination of both methods. The effectiveness of these solutions is evaluated by applying of a fluid–thermal interaction procedure. Results indicate that the reduction of heat flux on the blunt body persists when the spike length ratio of the double-aerodome model increases. The reduction then reaches a limit, beyond which an abnormal increase occurs due to the reattachment of streamlines onto the spike. In the case of jet on the single-aerodome model, a higher jet pressure ratio delivers a higher level of heat flux reduction. However, the excessive embedment of the jet into the recirculation zone tends to weaken the effectiveness of thermal protection. In addition, the heat flux can be further reduced by over 45% by introducing a cooling jet on the double-aerodome model. The combination of the two approaches also provides additional jet setting options, depending on the role of hypersonic vehicles. More importantly, the improvement in thermal protection performance is not achieved at the expense of drag reduction performance. The maximum increase in drag coefficient is limited to 8.1%.

Coupled investigation on drag reduction and thermal protection mechanism induced by a novel combinational spike and multi-jet strategy in hypersonic flows

Drag and heat reduction strategy in hypersonic vehicle design has already attracted worldwide attention. In this paper, a novel combinational spike and multi-jet strategy has been proposed for the drag and heat reduction in hypersonic flows. The flow field induced by this novel strategy has been numerically investigated by an in-house code. High-resolution upwind scheme (AUSMPW) and SST k-ω turbulence model are employed in the code. The fluid-thermal interaction is considered by using the conjugate heat transfer (CHT) approach. In addition, the thrust produced by the opposing jet is taken into account in computing the total drag. The influences of the spike length-to-diameter ratio, jet pressure ratio and lateral jet location on the flow field, drag reduction and heat properties are investigated thoroughly. The numerical results reveal that this novel strategy has better drag and heat reduction efficiency of unit mass flow rate, and the negative thrust induced by the opposing jet proved to be an important factor for the total drag. The spike length-to-diameter ratio has a great influence on the drag reduction, and the drag coefficient decreases significantly as the spike length-to-diameter ratio increases. However, the Stanton number is less affected by the spike length-to-diameter ratio variation. The jet pressure ratio, including the pressure ratios of opposing jet and lateral jet, are the key parameters for the drag reduction and thermal protection, and both the drag coefficient and the Stanton number decrease significantly as jet pressure ratio rises. For the lateral jet location effect, it influences the flow features, drag reduction and thermal protection significantly. The drag coefficient can be reduced by nearly 20% as the lateral jet location increases from 0.1 to 0.7, and the peak value of the Stanton number increases sharply by 49.36% when the lateral jet location varies from 0.9 to 0.1.

Novel Combinational Aerodisk and Lateral Jet Concept for Drag and Heat Reduction in Hypersonic Flows

Hypersonic vehicles have attracted lasting and worldwide attention in recent years. Considerable aerodynamic drag and severe aerothermal loads are major challenges for hypersonic vehicles. A novel combinational aerodisk and lateral jet concept is proposed for drag reduction and thermal protection in hypersonic flows. The flow field characteristics have been numerically investigated with in-house code. The Reynolds-averaged Navier-Stokes (RANS) equations were adopted to simulate the flow field, and the shear stress transport (SST) k−ω turbulence model was used to present the turbulent nature. Fluid–thermal interaction is also taken into consideration in this paper. The influences of the lateral jet pressure ratio and its location on the flow field have been thoroughly studied using numerical methods. The obtained results demonstrate that the novel concept is beneficial for drag reduction and thermal protection in hypersonic flows. Increasing the lateral jet pressure ratio can further improve drag reduction performance. In addition, the heat flux can be significantly reduced by increasing the lateral jet pressure ratio. The lateral jet location also has important effects on the flow properties. The peak values of the Stanton number and wall static pressure can even be reduced by 19.76% and 22.15%, respectively, with different lateral jet locations.

Deviation analysis of loosely coupled quasi-static method for fluid-thermal interaction in hypersonic flows

Abstract Fluid-thermal interaction plays an important role in the design and development of hypersonic vehicles. Among the different ways to couple the flow field with the material thermal response, the loosely coupled quasi-static method is widely used. In this paper, deviation formulas based on one-dimensional model are derived for uncoupled method and loosely coupled quasi-static method to estimate the structural temperature deviations at the stagnation point in different forward time steps. To verify the formulas, fluid-thermal coupling numerical simulations are conducted for 2-D and 3-D hypersonic fluid-thermal interaction problems. The results show that the temperature deviation formulas agree quite well with the deviations from numerical simulation. The derived deviation formulas can serve as some guidance for selecting an appropriate forward time step for the loosely coupled quasi-static method.

Fluid–Thermal Interaction Investigation of Spiked Blunt Bodies at Hypersonic Flight Condition

A spiked blunt body flying at hypersonic speed could result in significant thermal interactions between the external flowfield and the internal structure, which have not received enough attention in previous investigations. In the present study, time-dependent, loosely coupled fluid–thermal interaction simulations are conducted on a blunt body equipped with a spike with variable length at a , flight condition. The results show that, in the range of time considered in the study, a blunt body with a longer spike yields a better dynamic thermal performance, that is, a lower peak temperature on the blunt forebody surface and a slower temperature rise both on the forebody surface and inside the structure can be obtained. In addition, various levels of drag coefficient drop can be observed during the coupling process. A maximum decrease of 5.7% is achieved among the investigated models. The study reveals the necessity of the coupled fluid–thermal analysis to accurately predict the aerothermal environment of the spiked blunt body and to capture the variation of aerodynamic force, which is critical for structural design and flight control system, respectively.

Topology optimization for fluid–thermal interaction problems under constant input power

This paper deals with density-based topology optimization considering fluid and thermal interactions, in which the Navier---Stokes and heat transport equations are coupled. We particularly focus on designing heat exchangers. In the engineering context, heat exchangers are designed while considering a certain amount of input power. Therefore it is important to maximize the performance of a heat exchanger under a constant input power. In this paper we propose a way to control the input power by introducing an extra integral equation. To be more precise, in the fluid analysis, the inlet pressure is determined by solving the extra integral equation together with the Navier---Stokes equation. By doing this we can keep the inlet power constant even when the flow channels are changed in the optimization process. Consequently, the system of equations of the fluid field takes an integrodifferential form. On the other hand, in the heat transport analysis, a single governing equation is defined for simultaneously modeling both the solid and fluid parts. The design variable is a fluid fraction whose distribution represents the topology of the solid and fluid domains. When designing heat exchangers, two different heat conditions are considered in the formulation of the optimization problems, namely temperature-dependent and temperature-independent heat sources. Through the numerical examples for designing flow channels in a heat exchanger, it is shown that distinct topologies can be obtained according to the input power and the heat source conditions.