Prediction of transients and control reactions in a transonic wind tunnel

Abstract

This work describes a lumped parameter mathematical model for the prediction of transients in an aerodynamic circuit of a transonic wind tunnel. Control actions to properly handle those perturbations are also assessed. The tunnel circuit technology is up to date and incorporates a novel feature: high-enthalpy air injection to extend the tunnel’s Reynolds number capability. The model solves the equations of continuity, energy and momentum and defines density, internal energy and mass flow as the basic parameters in the aerodynamic study as well as Mach number, stagnation pressure and stagnation temperature, all referred to test section conditions, as the main control variables. The tunnel circuit response to control actions and the stability of the flow are numerically investigated. Initially, for validation purposes, the code was applied to the AWT ("Altitude Wind Tunnel" of NASA-Lewis). In the sequel, the Brazilian transonic wind tunnel was investigated, with all the main control systems modeled, including injection

Mathematical Modeling of Wind-Tunnel Thermal Behavior

“…Development of a mathematical model for the behavior of a wind tunnel loosely follows the "lumped parameter" approach outlined in [1,9]. The approach begins by dividing the wind tunnel into sections (see Fig.…”

“…This term can be solved explicitly by integrating with respect to time, such that the mass flow rate in response to a fan speed acceleration changes as a function of both time and position around the wind-tunnel circuit. Examples of this kind of solution for several different closed-circuit wind tunnels are given in [1,9,10].…”

“…M ATHEMATICAL models for the behavior of wind tunnels and test facilities have been developed for a variety of reasons [1][2][3][4][5][6][7][8]. For example, in [1], a mathematical model of a new wind tunnel was developed to ensure that the facility would achieve its target test envelope.…”

“…For example, in [1], a mathematical model of a new wind tunnel was developed to ensure that the facility would achieve its target test envelope. Mathematical models have also been used to investigate upgrades to existing facilities or their modification for new test missions [2], to aid in the development of more efficient test scheduling procedures [3], to investigate facility behavior for new test procedures, or to train facility operators [4].…”

“…Mathematical models are typically developed from basic fluidmechanic equations; however, the fundamental purpose of the models described in [1][2][3][4][5][6][7][8] is to provide rapid time-accurate predictions for the response of the full wind tunnel to changes in test conditions or control settings. As such, approximations or simplifications to the basic equations are incorporated to handle the large physical scale of the problem with satisfactory computational expense.…”