Scale-Resolving Simulations of a Circular Cylinder Subjected to Low Mach Number Turbulent Inflow

Abstract

Inflow turbulence is relevant for many engineering applications relating to noise generation, including aircraft wings, landing gears, and non-cavitating marine propellers. While modelling of this phenomenon is well-established for higher Mach number aerospace problems, lower Mach number applications, which include marine propellers, still lack validated numerical tools. For this purpose, simplified cases for which extensive measurement data are available can be used. This paper investigates the effect of inflow turbulence on a circular cylinder at a Reynolds number of 14,700, a Mach number of 0.029, and with inflow turbulence intensities ranging between 0% and 22%. In the present work focus is put on the hydrodynamics aspect, with the aim of addressing radiated noise in a later study. The flow is simulated using the partially averaged Navier Stokes equations, with turbulence inserted using a synthetic inflow turbulence generator. Results show that the proposed method can successfully replicate nearfield pressure variations and relevant flow features in the wake of the body. In agreement with the literature, increasing inflow turbulence intensity adds broadband frequency content to all the presented fluctuating flow quantities. In addition, the applied variations in inflow turbulence intensity result in a major shift in flow dynamics around a turbulence intensity of 15%, when the dominant effect of von Kármán vortices on the dominant flow dynamics becomes superseded by freestream turbulence.

How accurate are ultrasonic anemometers, calibrated in a laminar wind tunnel, under turbulent conditions?

“…For instance, [5] identified the sensitivity of the wake behind the probe heads' supporting structures to the characteristics of the approaching flow as a potential factor that could render the calibration invalid. This is because the 'ideal' wake resulting from the laminar stationary flow is deformed [15]. The analysis results for the TriSonica Mini (see Figure 6b) show a less pronounced trend of under-or overestimation of the wind speed for turbulence level, with a variance of approximately 0.22 m 2 /s 2 for low turbulence and 0.039 m 2 /s 2 for grid turbulence.…”

Visualization of Underwater Radiated Noise in the Near- and Far-Field of a Propeller-Hull Configuration Using CFD Simulation Results

“…A considerable research effort is going into improving the accuracy of finite volume CFD simulations including the turbulence scale-resolved modeling to be able to evaluate the comparatively small pressure fluctuations in a fluid dynamic context as sound waves. Fundamental investigations dealing with the sound emitted by cylinders by resolving some scales of turbulence have been successful in accurately predicting pressure fluctuations [3] and utilized acoustic analogies, such as the Ffowcs-Williams-Hawkings (FWH) acoustic analogy in its permeable surface formulation [4], to simulate sound propagation while maintaining the incompressibility assumption for the fluid medium [5]. This fluid simulation methodology is also applied to more complex geometries with some success, such as for propellers in open water conditions [6] and inclined flow with obstacles in the propeller slipstream [7], where the main challenge in the accurate prediction of underwater noise is identified as resolving the cavitating tip vortex using adaptive mesh refinement technique.…”