Fundamental Study of Hybrid Wind Tunnel Integrating Numerical Simulation and Experiment in Analysis of Flow Field

Abstract

This paper deals with a new flow analysis system, namely the hybrid wind tunnel, which integrates the experimental measurement with a wind tunnel and a corresponding numerical simulation with a computer. Analysis here is performed for the fundamental flow with the Karman vortex street in a wake of a square cylinder. A specific feature of the hybrid wind tunnel is existence of the feedback signal to compensate the error in the pressure on the side walls of the cylinder and the feed-forward signal to adjust the upstream velocity boundary condition. Investigation is focused on evaluating the hybrid wind tunnel as a flow analysis methodology with respect to the ordinary simulation and the experiment. As compared with the ordinary simulation, the hybrid wind tunnel substantially improves the accuracy and the efficiency in the analysis of the flow. Especially, the oscillation of the flow due to the Karman vortex street reproduced with the hybrid wind tunnel exactly synchronizes with that of the experiment, while that with the ordinary simulation never behave like that. In comparison with the experiment, the hybrid wind tunnel provides more detailed information of the flow than the experiment does.

A Review of Measurement-Integrated Simulation of Complex Real Flows

“…Comparison of the Kalman filter and state observer shows that the latter has a simpler structure and retains an essential part of the state estimation. The present author [13] proposed a measurement-integrated simulation (hereafter abbreviated as "MI simulation"), which is a kind of observer using a CFD scheme as the mathematical model of a relevant system, and successfully applied it to a turbulent flow in a square duct, a Karman vortex street behind a square cylinder [14] [15], and blood flow in an aneurismal aorta [16].…”

“…In Section 2, formulations of MI simulation are presented, including governing equations of an observer for a flow field, those of a linearized error dynamics describing the convergence of the observer [21], and stabilization of the numerical scheme, which is important in implementation of MI simulation [22]. Applications of MI simulation presented in Section 3 range from fundamental turbulent pipe flows [1] [13] [23] and Karman vortices in a wind tunnel [14] [24] to clinical application to diagnosis of blood flows in a human body [16] [25]- [27].…”

Numerical Study on Variation of Feedback Methods in Ultrasonic-Measurement-Integrated Simulation of Blood Flow in the Aneurysmal Aorta

“…In other fields, Hayase et al applied flow observer to a turbulent flow through a square duct (16) , and Nisugi et al developed a hybrid wind tunnel and investigated the flow with a Karman vortex street (17), (18) . Note that, the UMI simulation treated in this paper is different from the authors' other work on turbulent flow or Karman vortex street mentioned above in the respect that the present work assumes incorrect boundary condition.…”

Fundamental Study of Ultrasonic-Measurement-Integrated Simulation of Real Blood Flow in the Aorta

“…9,17 Hayase et al proposed such a flow observer as an analytic methodology for general flow problems. 9 Conceptually, a flow observer is the state observer in control theory applied to flow analysis.…”

“…Nisugi et al developed a hybrid wind tunnel based on a flow observer and investigated the flow with a Karman vortex street, revealing the substantial advantage of such methodology over ordinary simulation, especially in its ability to reconstruct real flow and in its computational efficiency. 17 As a flow analysis method, a flow observer generally has several advantages: (1) simulation is performed using real flow conditions, (2) the simulation is simultaneously validated by measurement, and (3) real-time simulation can possibly be carried out owing to a significant improvement in computational efficiency.…”