Numerical Study of the Injection Process in a Transonic Wind Tunnel—Part I: The Design Point

[+] Author and Article Information
João B. P. Falcão Filho

 CTA–Aeronautics and Space Institute, São José dos Campos, SP 12228-900, Braziljb.falcao@ig.com.br

Marcos A. Ortega

 ITA–Technological Institute of Aeronautics, São José dos Campos, SP 12228-900, Brazilortega@ita.br

J. Fluids Eng 129(6), 682-694 (Dec 05, 2006) (13 pages) doi:10.1115/1.2734236 History: Received June 19, 2006; Revised December 05, 2006

Injectors are to be installed in a transonic wind tunnel with the ultimate objective of expanding the Reynolds number envelope. The aim of this research effort is to numerically simulate the steady mixing process involving the supersonic jets and the tunnel subsonic main stream. A three-dimensional, Reynolds-averaged Navier–Stokes numerical code was developed following the main lines of the finite-difference diagonal algorithm, and turbulence effects are accounted for through the use of the Spalart and Allmaras one-equation scheme. This paper focuses on the “design point” of the tunnel, which establishes (among other specifications) that the static pressures of both streams at the entrance of the injection chamber are equal. Three points are worth noting. The first is related to the numerical strategy that was introduced in order to mimic the real physical process in the entire circuit of the tunnel. The second corresponds to the solution per se of the three-dimensional mixing between several supersonic streams and the subsonic main flow. The third is the calculation of the “engineering” parameters, that is, the injection loss factor, gain, and efficiency. Many interesting physical aspects are discussed, and among them, the formation of three-dimensional shocks’ and expansions’ “domes”

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

PTT operational envelope; test section conditions

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Figure 2

Tunnel plenum chamber showing the injectors section and feeding system: (a) transition/injection chamber; (b) lateral view; and (c) inlet section

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Figure 3

Three-dimensional sketch of the simplified geometrical form of the mixing chamber. The domain of calculation is illustrated as the shadowed quarter volume. Also shown is the basic Cartesian reference system.

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Figure 4

Calculation cell at a cross section of the injection chamber

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Figure 5

Nodes distributions at the inlet face of subgrid E

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Figure 6

Domain of calculation for the shock-wave/boundary-layer interaction

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Figure 7

Static pressure field for the shock-wave/turbulent boundary-layer problem. Values are made dimensionless by the inlet pressure. Coordinates are given in meters.

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Figure 8

Pressure distribution on the flat plate wall

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Figure 9

Sketch of the experimental setup of Goebel and Dutton (23)

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Figure 10

Mixing layer thickness variation and db∕dx in the growth region

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Figure 11

Normalized mean streamwise velocity at the mixing region. Longitudinal position, x=0.10m.

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Figure 12

Test section stagnation pressure variation as a result of the injection process. The injectors’ stagnation pressure is set to the design condition (547kPa).

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Figure 13

Special lines definition at the entrance plane of the mixing chamber. Static pressure plots along these lines will illustrate the condition at the design point.

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Figure 14

Static pressure distributions along Lines 1, 3, 5, 6, and 7. Values are made dimensionless by the static pressure of the main stream at the entrance plane. Thin lines mark injectors’ walls positions.

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Figure 15

Static pressure fields in regions close to Injector 1: (a) vertical plane; and (b) horizontal plane. The solid black rectangles at the left of the plots mark the position of the injector. Coordinates are given in meters.

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Figure 16

Mach number fields: (a) on a vertical plane containing Line 3 (Fig. 1); (b) on a horizontal plane containing the geometrical centers of the injectors. The thick solid line at the bottom indicates the tunnel lateral wall. Coordinates are given in meters.

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Figure 17

Isolines of turbulent viscosity on a horizontal plane containing Line 6 (Fig. 1). Coordinates in meters.

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Figure 18

Isolines of stagnation pressure at the entrance plane. Coordinates in meters.

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Figure 19

Streamwise velocity profiles on vertical (a) and horizontal (b) planes containing the geometrical center of the injector 1. Coordinates in meters.

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Figure 20

Streamwise velocity profiles on a vertical plane containing the geometrical center of injector 1. Representation at the exit of the injection chamber. The dashed line represents the injector height. Coordinates in meters.

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Figure 21

Turbulent viscosity field on a horizontal plane passing by the geometrical center of the injectors’ exit sections. Coordinates in meters.

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Figure 22

Three-dimensional view of the jets development along the length of the mixing chamber




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