Effect of local heat supply to a turbulent boundary layer on the friction

Казаков, А. В.; Коган, М. Н.; Kuryachii, A. P.

doi:10.1007/bf02697935

Cited by 10 publications

(5 citation statements)

References 5 publications

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“…This increase in wall temperature causes the density at the wall to decrease in turn increasing the boundary layer height [4]. An increase in boundary layer height suggests a decrease in velocity gradient and again when analysing equation 2.1 it is seen that the friction coefficient would decrease [19].…”

Section: Boundary Layer Combustionmentioning

confidence: 98%

Section: Boundary Layer Combustionmentioning

confidence: 99%

“…Boundary layer combustion is when fuel is injected into the boundary layer under conditions suitable for combustion [19]. Boundary layer combustion causes large amounts of heat to be released which increases the temperature of flow near the wall [19]. This increase in wall temperature causes the density at the wall to decrease in turn increasing the boundary layer height [4].…”

Section: Boundary Layer Combustionmentioning

confidence: 99%

“…Kazakoz et al (1997) put forward the explanation that the increase in temperature of the flow would increase the viscosity of the flow. They stated that the effects of the increased boundary layer height and decreased velocity profile out weighed the increase in viscosity hence why the total friction coefficient decreased [19]. Kazakoz (1997) also observed that the boundary layer height did not return to its original size until far down stream of the injector and that this aligned with the "long memory" effect [19].…”

Section: Boundary Layer Combustionmentioning

confidence: 99%

“…They stated that the effects of the increased boundary layer height and decreased velocity profile out weighed the increase in viscosity hence why the total friction coefficient decreased [19]. Kazakoz (1997) also observed that the boundary layer height did not return to its original size until far down stream of the injector and that this aligned with the "long memory" effect [19]. Kazakov et al (1997) suggested that friction reduction due to boundary layer combustion was only due to the density decrease meaning that the friction reduction would be the same regardless of the flow regime [19].…”

Section: Boundary Layer Combustionmentioning

confidence: 99%

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UQ eSpace

Hopkins¹

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To enable economical access to space through the use of an air breathing engine, major technical hurdles need to be overcome; in particular, skin friction drag. Skin friction drag can be reduced by film cooling or boundary layer combustor. But the main problem is using a technique which is able to sustain a sufficient amount of fuel in the boundary layer for both these mechanism to occur. Porous injectors are the most promising method to inject fuel into the boundary layer. However there is currently a gap in the literature on how to model them in Eilmer4. The porous injector was modelled by two different methods. The first method, a more simple approach, looked at setting a constant hydrogen inflow boundary condition along the edge of the combustor. The second method, a more realistic approach, used a user-defined fluid block which separated a high pressure hydrogen reservoir and the combustor. It was found that both these methods can model porous injectors in Eilmer4. It was also found that porous injectors are able to eliminate skin friction completely along the face of the combustor due to the zero velocity gradient along the length of the wall in the direction to the centre of the combustor. The porous injector is able to replenish the fuel faster than the crosswind is able to rip it off the wall. The relevance of this investigation is that it provides confidence in modelling porous injectors in Eilmer4 as well as gaining a new understanding on the skin friction reduction effects of a porous injector.

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Section: Boundary Layer Combustionmentioning

confidence: 98%

Section: Boundary Layer Combustionmentioning

confidence: 99%

Section: Boundary Layer Combustionmentioning

confidence: 99%

Section: Boundary Layer Combustionmentioning

confidence: 99%

Section: Boundary Layer Combustionmentioning

confidence: 99%

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UQ eSpace

Hopkins¹

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Influence of distributed hydrogen injection and combustion on supersonic boundary layer stability and transition

Lysenko,

Gaponov,

Smorodsky

et al. 2023

Physics of Fluids

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This theoretical study recorded the influence of the distributed injection of hydrogen through a permeable surface and its combustion on the stability and transition of a supersonic boundary layer (BL). The laminar base flow for a multicomponent flat-plate BL was computed using the computational fluid dynamics solver with finite-rate chemistry for free-stream Mach number (M) = 2. Linear stability theory (LST) equations for a reactive gas mixture were derived in the local parallel base flow approximation. Stability calculations based on the developed theory revealed the possibility of a decrease in the local spatial amplification rates of unstable perturbations. A double reversal in the maximal amplification rate magnitudes of perturbations was obtained, wherein at first, they increased, then decreased to zero, and then rose again. The influence of the distributed injection and combustion of hydrogen in the supersonic BL on the position of the laminar-turbulent transition was estimated using the LST-based eN-method. Calculated and experimentally obtained dependencies of the relative transition Reynolds number on the relative mass flow rate of injected hydrogen were compared. It was found that depending upon the flow conditions, the hydrogen diffusion flame could accelerate or decelerate the transition in the supersonic M = 2 BL, when compared to absence of hydrogen burning. Two counteracting effects compete: heat supply by combustion exerts stabilizing influence, while low-molecular-weight gas blowing from the surface exerts destabilizing influence. Depending on the interplay of these two factors, it would be possible to obtain acceleration or deceleration of transition.

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Influence of the position and energy of local rapid heating of the supersonic gas flow on the position of the separation point on the surface of airfoil

Saveliev

2021

J. Phys.: Conf. Ser.

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Using numerical simulation, the study of the process of rapid local energy release in supersonic flow in a two-dimensional unsteady case and the process of separation point shift by a gas-dynamic perturbation caused by the energy input into the flow were carried out. The flow around the airfoil was modeled as laminar, and local heat release as a instantaneous isochoric process without changing the gas density. The value of energy input and the place of gas heating on the surface of the airfoil were varied. The cases of initiation of energy input at a certain distance before and after the initial position of the separation point, as well as immediately before the separation point, were considered. During obtained flow patterns processing, the displacement of the separation point position downstream, the time of this displacement, the position and size of the separation region with reattachment and the lifetime of this flow zone were determined. The obtained data can help to choose a strategy for initiating energy input in a repetitively pulsed regime, as well as in a regime of a variable position of energy release on the surface of a body, streamlined by compressible gas flow.

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Effect of local heat supply to a turbulent boundary layer on the friction

Cited by 10 publications

References 5 publications

UQ eSpace

UQ eSpace

Influence of distributed hydrogen injection and combustion on supersonic boundary layer stability and transition

Influence of the position and energy of local rapid heating of the supersonic gas flow on the position of the separation point on the surface of airfoil

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