• Acta Physica Sinica
  • Vol. 68, Issue 22, 224701-1 (2019)
Chang-Gen Lu*, Lu-Yu Shen, and Xiao-Qing Zhu
DOI: 10.7498/aps.68.20190684 Cite this Article
Chang-Gen Lu, Lu-Yu Shen, Xiao-Qing Zhu. Numerical study of effect of pressure gradient on boundary-layer receptivity under localized wall blowing/suction[J]. Acta Physica Sinica, 2019, 68(22): 224701-1 Copy Citation Text show less

Abstract

Boundary-layer receptivity is the initial stage of the laminar-turbulent transition process, and plays a key role in predicting and controlling the transition. The present researches indicate that the boundary-layer receptivity is affected not only by the different sorts of free-stream disturbances or the size, shape and position of the wall localized roughness and blowing/suction, but also by the pressure gradient. Therefore, the local receptivity under the interaction between the free-stream turbulence and localized wall blowing/suction in the pressure-gradient boundary layer is studied in the present work, thus revealing the effect of the pressure gradient on the receptive process and the group speeds of the excited T-S wave packets under the interaction of the free-stream turbulence with localized wall blowing/suction in the boundary layer. High-order finite difference scheme is utilized to discretize the incompressible perturbation Navier-Stokes equation. A modified fourth-order Runge-Kutta scheme is used for time integration. The compact difference scheme based on non-uniform meshes is applied to the spatial discretization. The convective term is discretized by the fifth-order upwind compact scheme. The pressure gradient term is discretized by the sixth-order symmetric compact scheme. The viscosity term is discretized by the fifth-order symmetric compact scheme. Besides, the pressure Poisson equation is solved by the fourth-order scheme on the non-uniform meshes. The favorable or adverse pressure gradient promotes or suppresses the receptivity triggered by the interaction between free-stream turbulence and blowing/suction. And the blowing always induces a stronger receptivity than the suction in the same intensity. The initial amplitude of the T-S wave and wave packet excited in the adverse-pressure-gradient boundary layer are two orders larger than those excited in the favorable-pressure-gradient boundary layer. It is analyzed in detail that the favorable and adverse pressure gradient play a promoting or suppressing role in the growth of the excited T-S wave. Then the influences of the pressure gradient on the amplitudes, growth rates, wave numbers, phase speeds and shape functions of the excited T-S waves are investigated. The intensive research on receptivity in the pressure-gradient boundary layers provides a reference for designing the turbine machinery blades in the practical engineering.
$\left\{ \begin{aligned} & \nabla \cdot {{V}} = 0, \\ & \frac{{\partial {{V}}}}{{\partial t}} + \left( {{{V}} \cdot \nabla } \right){{V}} = - \nabla p + \frac{1}{{Re}}{\nabla ^2}{{V}} , \end{aligned} \right.$(1)

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$\begin{split}{{{u}}_\infty } =\, & \left( \begin{aligned} {u_\infty } \\ {v_\infty } \end{aligned} \right) = \varepsilon \sum\limits_{{{m}} = - {{M}}}^M \sum\limits_{j = - J}^J \left( \begin{aligned} {{\hat u}_\infty } \\ {{\hat v}_\infty } \end{aligned} \right)\\ & \times{\rm{exp}}\left[ {{\rm i}\left( {m{\kappa _1}x + {{j}}{\kappa _2}y - m{\kappa _1}t} \right)} \right], \end{split}$(2)

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$ \left\{ \begin{aligned} & {{\hat u}_\infty } = {\rm i}\frac{{m{\kappa _1}{\rm{j}}{\kappa _2}}}{{\kappa \sqrt {{m^2}{\kappa _1}^2} }} \cdot \sqrt {\frac{{2E\left( \kappa \right){\kappa _1}{\kappa _2}}}{{4{\text{π}}{\kappa ^2}}}} \cdot {{\rm{e}}^{{\rm i}\sigma }}, \\ & {{\hat v}_\infty } = - {\rm i}\frac{{\sqrt {{m^2}{\kappa _1}^2} }}{\kappa } \cdot \sqrt {\frac{{2E\left( \kappa \right){\kappa _1}{\kappa _2}}}{{4{\text{π}}{\kappa ^2}}}} \cdot {{\rm{e}}^{{\rm i}\sigma }}, \end{aligned} \right. $ ()

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$v\left( {{x_w},0} \right) = q,$(3)

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$ {A_{{\rm{FST}}}} = \sqrt {\overline {{u_{{\rm{FST}}}}^2} + \overline {{v_{{\rm{FST}}}}^2} }, $ (4)

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$ {A_R} = \sqrt {\overline {{u_R}^2} + \overline {{v_R}^2} }, $ (5)

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$ {A_{{\rm{TS}}}} = \sqrt {\overline {{u_{{\rm{TS}}}}^2} + \overline {{v_{{\rm{TS}}}}^2} }, $ (8)

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Chang-Gen Lu, Lu-Yu Shen, Xiao-Qing Zhu. Numerical study of effect of pressure gradient on boundary-layer receptivity under localized wall blowing/suction[J]. Acta Physica Sinica, 2019, 68(22): 224701-1
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