Comparison of unsteady pressure fields on turrets with different surface features using pressure-sensitive paint

Modal Analysis of the Surface Pressure Field Around a Hemispherical Turret using Pressure Sensitive Paint

“…The first two modes are "wake shifting" modes at both M = 0.55 and M = 0.65. This "wake shifting" has an anti-symmetric character on the turret itself, as schematically shown in Figure 7, and was observed in prior PSP experiments [3,27]. The "wake shifting" is likely caused by very large structures shed off alternating sides of the turret [27].…”

“…The pressure field on the surface of the turret has been extensively studied in the past and the experiment presented in this paper is a follow up on previous work using PSP [3,18]. The surface pressure field on the turret carries both the signature of the turbulent structures in the turret's vicinity and any global pressure modes over the turret.…”

“…There has been extensive experimental work done to study these hemispherical turrets in the last decade. This work includes characterizing both the aerodynamic [1,2,3] and aero-optic [4,5,6] performance of the flow around the turrets at subsonic and transonic speeds. In addition to these experimental studies, there have been extensive CFD studies into the flow around hemispherical turrets [7,8,9,10,11].…”

“…POD naturally generates a set of basis vectors that maximizes the amount of energy per mode and thus is useful for locating where most of the "energy" in the flow is located. It is also useful for filtering out high spatial frequency modes [3], which are usually noisy. Dynamic Mode Decomposition (DMD) [22,23,24], on the other hand, decomposes the flow into a series of periodic modes at given frequencies.…”

Modal Analysis of Fluid Flows: An Overview

“…POD has been the bedrock of modal decomposition techniques to extract coherent structures for unsteady fluid flows. To address some of the shortcomings of standard POD analysis, many variations have emerged; namely the Balanced POD [76] (see Section IV), Split POD [77], Sequential POD [78,79], Temporal POD [80], and Joint POD [81], amongst others. A number of overarching studies have emerged to bridge the gap between POD and other decomposition methods, revisiting some of the early POD discussions by Lumley [27] and George [63].…”