Free-surface flow due to impulsive motion of a submerged circular cylinder

1995 ◽  
Vol 286 ◽  
pp. 67-101 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Hydrodynamic Force ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Constant Acceleration ◽  
Impulsive Motion ◽  
Gravitational Effects ◽  
Bipolar Coordinates

The impulsively starting motion of a circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The series expansion is taken as far as necessary to include the leading gravitational effects for two cases: constant velocity and constant acceleration, both commencing from rest. The hydrodynamic force on the cylinder and the surface elevation are calculated and expressed in terms of bipolar coordinates. Comparisons are also made with earlier theoretical and experimental work. The theory is valid for arbitrary value of submergence depth to cylinder radius.

Free-surface flow generated by a small submerged circular cylinder starting from rest

1995 ◽  
Vol 286 ◽  
pp. 103-116 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Hydrodynamic Force ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Third Order ◽  
Force Prediction ◽  
Small Cylinder ◽  
Submergence Depth

The impulsively starting motion of a small circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The cylinder is considered small if the ratio between its radius and initial submergence depth is much smaller than one. The surface elevation is calculated up to third order. The hydrodynamic force on the small cylinder is also discussed. Certain inconsistencies in our small-cylinder approximation (assuming locally uniform flow around the cylinder) are found in the force prediction. The present work is an accompanying paper to Tyvand & Miloh (1995), where the same problem is studied for arbitrary radius versus submergence depth.

Nonlinear free-surface flow due to an impulsively started submerged point sink

1998 ◽  
Vol 364 ◽  
pp. 325-347 ◽  
Author(s):  
MING XUE ◽  
DICK K. P. YUE
Keyword(s):  
Free Surface ◽  
Steady State ◽  
Numerical Study ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Boundary Integral ◽  
Critical Regime ◽  
Gravitational Acceleration ◽  
Nonlinear Free Surface

The unsteady fully nonlinear free-surface flow due to an impulsively started submerged point sink is studied in the context of incompressible potential flow. For a fixed (initial) submergence h of the point sink in otherwise unbounded fluid, the problem is governed by a single non-dimensional physical parameter, the Froude number, [Fscr ]≡Q/4π(gh5)1/2, where Q is the (constant) volume flux rate and g the gravitational acceleration. We assume axisymmetry and perform a numerical study using a mixed-Eulerian–Lagrangian boundary-integral-equation scheme. We conduct systematic simulations varying the parameter [Fscr ] to obtain a complete quantification of the solution of the problem. Depending on [Fscr ], there are three distinct flow regimes: (i) [Fscr ]<[Fscr ]1≈0.1924 – a ‘sub-critical’ regime marked by a damped wave-like behaviour of the free surface which reaches an asymptotic steady state; (ii) [Fscr ]1<[Fscr ]<[Fscr ]2≈0.1930 – the ‘trans-critical’ regime characterized by a reversal of the downward motion of the free surface above the sink, eventually developing into a sharp upward jet; (iii) [Fscr ]>[Fscr ]2 – a ‘super-critical’ regime marked by the cusp-like collapse of the free surface towards the sink. Mechanisms behind such flow behaviour are discussed and hydrodynamic quantities such as pressure, power and force are obtained in each case. This investigation resolves the question of validity of a steady-state assumption for this problem and also shows that a small-time expansion may be inadequate for predicting the eventual behaviour of the flow.

Nonlinear Free-Surface Flow Around an Impulsively Moving Cylinder

1989 ◽  
Vol 33 (03) ◽  
pp. 194-202
Author(s):  
Keh-Han Wang ◽  
Allen T. Chwang
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Surface Elevation ◽  
Cylinder Surface ◽  
Cylinder Wall ◽  
Free Surface Elevation ◽  
Moving Cylinder ◽  
Nonlinear Free Surface

Nonlinear free-surface flow around an impulsively accelerating, vertical surface-piercing cylinder is investigated analytically. The exact solutions for the velocity potential and free-surface elevation are derived up to the third order by the small-time-expansion method. The hydrodynamic pressure acting on the cylinder wall is also obtained. A constant horizontal acceleration is considered to illustrate our theoretical results. It is found that, during the initial stage of this impulsive motion, no travelling free-surface waves are present. A surge of water appears on the upwind face and a depression forms on the down-wind face. The second-order free-surface elevation is singular along the contact line between the fluid surface and the cylinder surface. The nonlinear pressure distribution on the cylinder surface has been determined.

scholarly journals Gravity-driven granular free-surface flow around a circular cylinder

2013 ◽  
Vol 720 ◽  
pp. 314-337 ◽  
Author(s):  
X. Cui ◽  
J. M. N. T. Gray
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Numerical Simulations ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Pyroclastic Flows ◽  
Small Scale ◽  
Shallow Water Flows ◽  
Free Region ◽  
Gravity Driven

AbstractSnow avalanches and other hazardous geophysical granular flows, such as debris flows, lahars and pyroclastic flows, often impact on obstacles as they flow down a slope, generating rapid changes in the flow height and velocity in their vicinity. It is important to understand how a granular material flows around such obstacles to improve the design of deflecting and catching dams, and to correctly interpret field observations. In this paper small-scale experiments and numerical simulations are used to investigate the supercritical gravity-driven free-surface flow of a granular avalanche around a circular cylinder. Our experiments show that a very sharp bow shock wave and a stagnation point are generated in front of the cylinder. The shock standoff distance is accurately reproduced by shock-capturing numerical simulations and is approximately equal to the reciprocal of the Froude number, consistent with previous approximate results for shallow-water flows. As the grains move around the cylinder the flow expands and the pressure gradients rapidly accelerate the particles up to supercritical speeds again. The internal pressure is not strong enough to immediately push the grains into the space behind the cylinder and instead a grain-free region, or granular vacuum, forms on the lee side. For moderate upstream Froude numbers and slope inclinations, the granular vacuum closes up rapidly to form a triangular region, but on steeper slopes both experiments and numerical simulations show that the pinch-off distance moves far downstream.

scholarly journals Laminar free-surface flow into a vertical cylinder

1975 ◽  
Vol 3 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Thomas G. Smith ◽  
J.O. Wilkes
Keyword(s):  
Free Surface ◽  
Vertical Cylinder ◽  
Free Surface Flow ◽  
Surface Flow

Free-Surface Flow Simulations With Interactively Moving Bodies

2017 ◽  
Author(s):  
Arthur E. P. Veldman ◽  
Henk Seubers ◽  
Peter van der Plas ◽  
Joop Helder
Keyword(s):  
Free Surface ◽  
Free Fall ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Numerical Solution Method ◽  
Flow Simulations ◽  
Floating Object ◽  
Offshore Industry ◽  
Floating Objects ◽  
Moving Bodies

The simulation of free-surface flow around moored or floating objects faces a series of challenges, concerning the flow modelling and the numerical solution method. One of the challenges is the simulation of objects whose dynamics is determined by a two-way interaction with the incoming waves. The ‘traditional’ way of numerically coupling the flow dynamics with the dynamics of a floating object becomes unstable (or requires severe underrelaxation) when the added mass is larger than the mass of the object. To deal with this two-way interaction, a more simultaneous type of numerical coupling is being developed. The paper will focus on this issue. To demonstrate the quasi-simultaneous method, a number of simulation results for engineering applications from the offshore industry will be presented, such as the motion of a moored TLP platform in extreme waves, and a free-fall life boat dropping into wavy water.

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