Direct Numerical Simulations of the Pulsating Flow over a Plane Wall

The results of direct numerical simulations of the flow generated in a plane duct by a pressure gradient which is the sum of two terms are described. The first term of the pressure gradient is constant in space but it oscillates in time whereas the second term is constant both in space and in time. Therefore, a pulsating flow is generated, similar to that generated at the bottom of a monochromatic propagating surface wave when nonlinear effects are taken into account. The simulations are carried out for values of the parameters similar to those considered in previous investigations. It is shown that even a small constant pressure gradient influences the flow regime in the bottom boundary layer. In particular, turbulence strength is damped when the steady velocity component has the direction opposite to the oscillating velocity component whereas turbulence strength increases when the steady and oscillating components point in the same direction. Even though the flow is not exactly equal to that generated at the bottom of sea waves, where second order effects in the wave steepness induce a steady streaming in the direction of wave propagation, our results provide information on the interaction of the steady streaming with the oscillatory flow and are also relevant for investigating the dynamics of sediment close to the sea bottom. Indeed, since the turbulent eddies tend to pick-up the sediment from the bottom, it can be inferred that the triggering of turbulence enhances sediment transport towards the shore.

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Direct Numerical Simulations of an Adverse Pressure Gradient Turbulent Boundary Layer on High Performance Computers

High Performance Computing in Science and Engineering ’99 ◽

10.1007/978-3-642-59686-5_28 ◽

2000 ◽

pp. 315-326 ◽

Cited By ~ 1

Author(s):

Michael Manhart

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Pressure Gradient ◽

Numerical Simulations ◽

High Performance ◽

Adverse Pressure Gradient ◽

Direct Numerical Simulations ◽

High Performance Computers

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Lifetimes of Rogue Wave Events in Direct Numerical Simulations of Deep-Water Irregular Sea Waves

Fluids ◽

10.3390/fluids4020070 ◽

2019 ◽

Vol 4 (2) ◽

pp. 70 ◽

Cited By ~ 4

Author(s):

Anna Kokorina ◽

Alexey Slunyaev

Keyword(s):

Numerical Simulations ◽

Heavy Tails ◽

Rogue Wave ◽

Probability Distributions ◽

Rogue Waves ◽

Direct Numerical Simulations ◽

Point Of View ◽

Sea Waves ◽

Physical Point ◽

Irregular Wave

The issue of rogue wave lifetimes is addressed in this study, which helps to detail the general picture of this dangerous oceanic phenomenon. The direct numerical simulations of irregular wave ensembles are performed to obtain the complete accurate data on the rogue wave occurrence and evolution. Purely collinear wave systems, moderately crested, and short-crested sea states have been simulated by means of the high-order spectral method for the potential Euler equations. As rogue waves are transient and poorly reflect the physical effects, we join instant abnormally high waves in close locations and close time moments to new objects, rogue events, which helps to retrieve the abnormal occurrences more stably and more consistently from the physical point of view. The rogue event lifetime probability distributions are calculated based on the simulated wave data. They show the distinctive difference between rough sea states with small directional bandwidth on one part, and small-amplitude sea states and short-crested states on the other part. The former support long-living rogue wave patterns (the corresponding probability distributions have heavy tails), though the latter possess exponential probability distributions of rogue event lifetimes and generally produce much shorter rogue wave events.

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A dynamic multi-scale approach for turbulent inflow boundary conditions in spatially developing flows

Journal of Fluid Mechanics ◽

10.1017/s0022112010005616 ◽

2011 ◽

Vol 670 ◽

pp. 581-605 ◽

Cited By ~ 47

Author(s):

GUILLERMO ARAYA ◽

LUCIANO CASTILLO ◽

CHARLES MENEVEAU ◽

KENNETH JANSEN

Keyword(s):

Boundary Layer ◽

Boundary Conditions ◽

Pressure Gradient ◽

Numerical Simulations ◽

Dynamic Method ◽

Adverse Pressure Gradient ◽

Direct Numerical Simulations ◽

Gradient Flows ◽

Multi Scale ◽

Turbulence Transition

A dynamic method for prescribing realistic inflow boundary conditions is presented for simulations of spatially developing turbulent boundary layers. The approach is based on the rescaling–recycling method proposed by Lund, Wu & Squires (J. Comput. Phys, vol. 140, 1998, pp. 233–258) and the multi-scale method developed by Araya, Jansen & Castillo (J. Turbul., vol. 10, no. 36, 2009, pp. 1–33). The rescaling process requires prior knowledge about how the velocity and length scales are related between the inlet and recycle stations. Here a dynamic approach is proposed in which such information is deduced dynamically by involving an additional plane, the so-called test plane located between the inlet and recycle stations. The approach distinguishes between the inner and outer regions of the boundary layer and enables the use of multiple velocity scales. This flexibility allows applications to boundary layer flows with pressure gradients and avoids the need to prescribe empirically the friction velocity and other flow parameters at the inlet of the domain. The dynamic method is tested in direct numerical simulations of zero, favourable and adverse pressure gradient flows. The dynamically obtained scaling exponents for the downstream evolution of boundary layer parameters are found to fluctuate in time, but on average they agree with the expected values for zero, favourable and adverse pressure gradient flows. Comparisons of the results with data from experiments, and from other direct numerical simulations that use much longer computational domains to capture laminar-to-turbulence transition, demonstrate the suitability of the proposed dynamic method.

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