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Mean and unsteady loading on square prisms with rounded edges: Hard marine growth, incidence, and Reynolds number effects

van Hinsberg, Nils (2021) Mean and unsteady loading on square prisms with rounded edges: Hard marine growth, incidence, and Reynolds number effects. Marine Structures (75). ISSN 0951-8339.

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Official URL: https://www.sciencedirect.com/science/article/pii/S0951833920301799

Abstract

A set of wind tunnel experiments was performed to study the average and fluctuating wind loading on an "infinite" 2D square prism with rounded edges of r/d = 0.16 for different heights of simulated hard marine growth at sub-to transcritical Reynolds numbers. It has already been shown, that a change in surface roughness from ks/d = 4.5x10-6 (smooth) to 1x10-3 (rough) on a similar prism at Alpha = 0deg and 45deg had large effects on the widths and the Reynolds numbers marking the boundaries of the various flow states. At Alpha = 45deg it furthermore led to a large Reynolds-number independency of the lift and drag forces and of the Strouhal number. For the present wind tunnel tests two additional values of ks/D were selected to obtain smaller increments in surface roughness: 4.5x10-4 (slightly rough) and 1.4x10-3 (very rough). Mean and fluctuating lift and drag forces, the main vortex shedding frequency, distributions of the mean surface pressures in the mid-span cross-section of the prism and the mean wake profiles were recorded simultaneously. The same two static angles of incidence, Alpha = 0deg and 45deg, were investigated for ReD = 60,000 to 12 million. For the prisms with smooth up to rough surfaces strong effects on the behaviour of all aerodynamic parameters with Reynolds number were found, whereas a further increase in ks/D induced hardly any additional effects. The absolute values of the aerodynamic parameters were found to be independent of a change in ks/D for the sub-to supercritical flow states. For the smooth and slightly rough prisms at Alpha = 0deg the supercritical flow state was present up to ReD = 12 million, whereas for the rougher prisms the upper transition and the transcritical flow states appeared at high Reynolds numbers. A change to alpha = 45deg induced little variation with ks/D for all aerodynamic coefficients. The overall behaviour of the force coefficients and the Strouhal number with ks/D and ReD were caused by motions of the transition, separation and reattachment locations.

Item URL in elib:https://elib.dlr.de/137481/
Document Type:Article
Title:Mean and unsteady loading on square prisms with rounded edges: Hard marine growth, incidence, and Reynolds number effects
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
van Hinsberg, NilsNils.vanHinsberg (at) dlr.deUNSPECIFIED
Date:January 2021
Journal or Publication Title:Marine Structures
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
ISSN:0951-8339
Status:Published
Keywords:bluff body; edge roundness; Reynolds number; flow separation; marine growth; aerodynamics; surface roughness; square prism
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Flight Physics (old)
Location: Göttingen
Institutes and Institutions:Institute of Aeroelasticity > Aeroelastic Experiments
Deposited By: van Hinsberg, Dr. Ir. Nils
Deposited On:24 Nov 2020 18:39
Last Modified:24 Nov 2020 18:39

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