Wave flume

About: Wave flume is a research topic. Over the lifetime, 1627 publications have been published within this topic receiving 23335 citations.

Introducing the TiDyWAVE field flume: A method to quantify natural ecosystem resilience against future storm waves

Abstract: Coastal ecosystems are increasingly threatened by global change. Insight in their resilience against increased storminess is needed for their application in nature‐based coastal defense schemes. This is often gained from flume experiments. Laboratory flumes provide excellent hydrodynamic control, but are restrictive in that it is extremely difficult to experiment on ecosystems with a naturally developed stability. Field flumes resolve the latter, but are limited to unidirectional currents. This study introduces an easily deployable field flume that mimics the near‐bed water motion of waves: the Tidal Dynamics WAVE flume (the TiDyWAVE). The hydrodynamics of the TiDyWAVE are assessed and compared to natural waves. We also compare it with a more traditional unidirectional flow channel by measuring the erodibility (ucr) of (1) bare sediments of which ucr can be calculated and (2) a seagrass meadow. The TiDyWAVE can generate peak oscillatory currents up to 0.32 m s−1 with a maximum wave period of 3.5 s, corresponding to 0.42 m high waves for a water depth of 3 m. ucr measurements showed that bed shear stress in the TiDyWAVE mimics field waves well. In accordance with theory, the observed ucr on bare sediment is consistently lower for oscillatory flow compared to unidirectional currents. On Thalassia testudinum, ucr under unidirectional currents increases 3.5 times faster with increasing blade area than under oscillatory flow. The difference in hydrodynamic sheltering of the seabed by flexible vegetation under currents vs. waves emphasizes the need for imposing representative hydrodynamics to study hydrodynamic thresholds of coastal ecosystems.

Performance Assessment of Three Turbulence Models Validated through an Experimental Wave Flume under Different Scenarios of Wave Generation

Abstract: This study aimed to adjust the turbulence models to the real behavior of the numerical wave flume (NWF) and the future research that will be carried out on it, according to the turbulence model that best adjusts to each particular case study. The k-e, k-ω and large-eddy simulation (LES) models, using the volume of fluid (VOF) method, were analyzed and compared respectively. The wavemaker theory was followed to faithfully reproduce the waves, which were measured in an experimental wave flume (EWF) and compared with the theory to validate each turbulence model. Besides, reflection was measured with the Mansard and Funke method, which has shown promising results when studying one of the most critical turbulent behaviors in the wave flume, called the breaking of the waves. The free surface displacement obtained with each turbulence model was compared with the recorded signals located at three points of the experimental wave flume, in the time domain of each run, respectively. Finally, the calculated reflection coefficients and the amplitudes of the reflected waves were compared, aiming to have a better understanding of the wave reflection process at the extinction zone. The research showed good agreement between all the experimental signals and the numerical outcomes for all the turbulence models analyzed.

Meshless Generalized Finite Difference Method for the Propagation of Nonlinear Water Waves under Complex Wave Conditions

Abstract: The propagation of nonlinear water waves under complex wave conditions is the key issue of hydrodynamics both in coastal and ocean engineering, which is significant in the prediction of strongly nonlinear phenomena regarding wave–structure interactions. In the present study, the meshless generalized finite difference method (GFDM) together with the second-order Runge–Kutta method (RKM2) is employed to construct a fully three-dimensional (3D) meshless numerical wave flume (NWF). Three numerical examples, i.e., the propagation of freak waves, irregular waves and focused waves, are implemented to verify the accuracy and stability of the developed 3D GFDM model. The results show that the present numerical model possesses good performance in the simulation of nonlinear water waves and suggest that the 3D “RKM2-GFDM” meshless scheme can be adopted to further simulate more complex nonlinear problems regarding wave–structure interactions in ocean engineering.

Wind/wave interactions in the surf zone

Abstract: Wind/wave interactions in the surf zone are studied using a wave tank and environmental wind tunnel. The wind simulation is achieved over a relatively short fetch using accelerated growth techniques at a scale of roughly 1:100. Waves are scaled at approximately 1:50, and consequently there is some scaling mis-match between the wind and wave simulations. Results show that wind has a significant effect on the breaking of the waves. Both breaker location and breaker type are shown to be affected by the wind. Results are in agreement with those of Douglass (1989 & 1990), who used a wind/wave flume to simulate the prototype conditions, but made no attempt to correctly simulate the turbulence in the air flow. The main findings, are that onshore winds promote spilling waves and increase the surf zone width, whereas offshore winds promote plunging waves, decreasing surf zone width. Hot-film measurements of the air flow over the waves show that there exists significant differences between the air flow structure of offshore and onshore winds over the surf zone. Under offshore winds, the surf zone exerts a large drag on the air flow, dramatically increasing turbulence intensities aerodynamic roughness z0, and friction velocity, u*, near the point of wave breaking. Under onshore winds the air flow is less affected and at the point of wave breaking, z0 for onshore winds is an order of magnitude lower than the value under offshore winds. Phase-averaging techniques indicate large wave-induced perturbations to the mean velocity over the waves, and these are present to heights of up to 5 or 6 times the breaker height over the point of wave breaking. Spectra indicate that for onshore winds large wave-frequency fluctuations are present at the shore. Additionally, studies of particle motion offshore of the surf zone indicate wind effects on the drift velocities of suspended particles, although the precise nature of the wind effect was not clear.

The initialization of nonlinear water waves in a numerical wave flume

Abstract: This study investigates the initialization of nonlinear free-surface simulations in a numerical wave flumeDue to the mismatch between the linear input wavemaker motion and the kinematics of fully nonlinear waves,direct numerical simulations of progressive waves,generated by a sinusoidally moving wavemaker,are prone to suffering from high-frequency wave instability unless the flow is given sufficient time to adjustA time ramp is superimposed on the wavemaker motion at the start that allows nonlinear free-surface simulations to be initialized with linear inputThe duration of the ramp is adjusted to test its efficiency for short waves and long wavesNumerical results show that the time ramp scheme is effiective to stabilize the wave instability at the start of the simulation in a wave flume