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On the evaluation of time-dependent fluid-dynamic forces on bluff bodies

Citation

Noca, Flavio (1997) On the evaluation of time-dependent fluid-dynamic forces on bluff bodies. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-08102005-132659

Abstract

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We present some exact expressions for the evaluation of time-dependent forces on a body in an incompressible and viscous cross-flow which only require the knowledge of the velocity field (and its derivatives) in a finite and arbitrarily chosen region enclosing the body.

Given a control volume V with external surface S which encloses an arbitrary body, the fluid-dynamic force F on the body can be evaluated from one of the following three expressions (in abbreviated form):

F = [...] + body motion terms,

F = [...] + body motion terms,

F = no volume integral terms + [...] + body motion terms, where N is the space dimension, u is the flow velocity, [...] is the vorticity, x is the position vector, and the tensors [...], [...], [...] depend only on the velocity field u and its (spatial and temporal) derivatives.

The first equation is already known for either simply connected domains or inviscid flows. We re-derive it here for viscous flows in doubly connected domains (i.e. domains which include a body). We then obtain the second and third equation through a simple algebraic manipulation of the first equation.

These expressions are particularly useful for experimental techniques like Digital particle Image Velocimetry (DPIV) which provide time sequences of 2D velocity fields but not pressure fields.

They are tested experimentally with DPIV on two-dimensional, low Reynolds number circular cylinder flows. Both steady and unsteady motions are studied.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Aerodynamic; bluff; DPIV; flow; fluid; forces; hydrodynamic; impulse; momentum; PIV; pressure; velocity; vorticity
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Roshko, Anatol
Thesis Committee:
  • Roshko, Anatol (chair)
  • Leonard, Anthony
  • Brennen, Christopher E.
  • Hornung, Hans G.
  • Gharib, Morteza
Defense Date:20 May 1997
Record Number:CaltechETD:etd-08102005-132659
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-08102005-132659
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3081
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:10 Aug 2005
Last Modified:26 Dec 2012 02:56

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