scholarly journals Steady Streaming Induced by Asymmetric Oscillatory Flows over a Rippled Bed

2020 ◽  
Vol 8 (2) ◽  
pp. 142
Author(s):  
Pietro Scandura ◽  
Carla Faraci ◽  
Paolo Blondeaux
Keyword(s):  
Boundary Layer ◽  
Water Waves ◽  
Bottom Boundary Layer ◽  
Steady Streaming ◽  
Geometrical Characteristics ◽  
Continuity Equations ◽  
Time Average ◽  
Harmonic Components ◽  
Rippled Bed ◽  
Steady Velocity

The flow induced by progressive water waves propagating over a rippled bed is reproduced by means of the numerical solution of momentum and continuity equations to gain insights on the steady streaming induced in the bottom boundary layer. When the pressure gradient that drives the flow is given by the sum of two harmonic components an offshore steady streaming is generated within the boundary layer which persists in the irrotational region. This steady streaming depends on the Reynolds number and on the geometrical characteristics of the ripples. Nothwithstanding the presence of a steady velocity component, the time-average of the force on the ripples vanishes.

Steady streaming in a turbulent oscillating boundary layer

2007 ◽  
Vol 571 ◽  
pp. 265-280 ◽  
Author(s):  
PIETRO SCANDURA
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Flow Rate ◽  
Stokes Equations ◽  
Infinite Plate ◽  
Harmonic Component ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Steady Streaming ◽  
Time Average

The turbulent flow generated by an oscillating pressure gradient close to an infinite plate is studied by means of numerical simulations of the Navier–Stokes equations to analyse the characteristics of the steady streaming generated within the boundary layer. When the pressure gradient that drives the flow is given by a single harmonic component, the time average over a cycle of the flow rate in the boundary layer takes both positive and negative values and the steady streaming computed by averaging the flow over n cycles tends to zero as n tends to infinity. On the other hand, when the pressure gradient is given by the sum of two harmonic components, with angular frequencies ω1 and ω2 = 2ω1, the time average over a cycle of the flow rate does not change sign. In this case steady streaming is generated within the boundary layer and it persists in the irrotational region. It is shown both theoretically and numerically that in spite of the presence of steady streaming, the time average over n cycles of the hydrodynamic force, acting per unit area of the plate, vanishes as n tends to infinity.

Mass transport under sea waves propagating over a rippled bed

1996 ◽  
Vol 314 ◽  
pp. 247-265 ◽  
Author(s):  
G. Vittori ◽  
P. Blondeaux
Keyword(s):  
Boundary Layer ◽  
Mass Transport ◽  
Outer Edge ◽  
Bottom Boundary Layer ◽  
Sea Waves ◽  
Bottom Boundary ◽  
Order Of Magnitude ◽  
Wave Slope ◽  
Rippled Bed ◽  
Sea Wave

Mass transport under a progressive sea wave propagating over a rippled bed is investigated. Wave amplitudes a* of the same order of magnitude as that of the boundary layer thickness δ* and of the ripple wavelength l* are considered. All the above quantities are assumed to be much smaller than the wavelength L* of the sea wave and much larger than the amplitude 2ε* of the ripples. The analysis is carried out up to the second order in the wave slope a*/L* and in the parameter ε*/δ* which is a measure of ripple steepness. Because of these assumptions, the slow damping of wave amplitude in the direction of wave propagation is taken into account. Attention is focused on the bottom boundary layer where an order (ε*/δ*)2 correction of the steady velocity components described by Longuet-Higgins (1953) is found. This correction persists at the outer edge of the bottom boundary layer and affects the solution in the entire water column.

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