Effect Of Vortex Shedding Research Articles

Aerodynamic Analysis of Simple Girder Bridges under Construction Phase

Bridge designs are becoming slender and lighter, making wind dynamic effects even more important than wind static effects. Some types of bridges show especially vulnerable situations during construction stages, when the structure is lighter or does not have its final stiffness. The aim of this document is to assess the dynamic wind loading on simple girder bridges during their construction phases. The studied section is formed by two steel beams supporting a concrete slab, but the analysis was made when the concrete slab has not been built yet. Several CFD simulations were made to find the aerodynamic parameters depending on the section’s dimensions. Three construction stages were analyzed: when only one beam is placed, when both beams are in their final locations but they are not connected yet, and when both beams are joined by the bracing. The results showed that vortex shedding effects are stronger in the along-wind direction due to the low horizontal bending stiffness of the beams and their large area perpendicular to the flow. Increasing beams’ distance is a good solution to reduce wind effects. However, closing the section with light plates was more effective, decreasing the frequency of vortex shedding and its effects.

Experimental and theoretical study on the internal pressure induced by the transient local failure of low-rise building roofs

A case study on the internal pressure induced by a local failure on the vulnerable gable roof of a low-rise building was extensively conducted experimentally and numerically. Five roof opening configurations were tested in the wind tunnel under three different boundary layer conditions, based on 1:40 scaled models. The effects of opening shape, opening position, opening ratio, building internal volume, and wind speed on peak transient and steady-state internal pressures were studied. The study results indicate that the peak transient and steady-state internal pressures and the corresponding transient overshoot ratio all increase with an increasing opening ratio. The peak steady-state internal pressure is little affected by the approaching wind speed; while the peak transient internal pressure coefficient shows a significant linear relationship with the wind speed. The coupling effect of vortex shedding and Helmholtz resonance in double building volume compensation situation may cause larger fluctuating internal pressure. Both the vortex shedding and Helmholtz resonance reduce the internal pressure coherence to some extent. The agreement between the numerical and experimental results is much better for the mean internal pressure than that for fluctuating internal pressure or peak internal pressure.

Can the ground enhance vertical force for inclined stroke plane flapping wing?

The numerical investigation of 2D insect wing kinematics in an inclined stroke plane is carried out using an immersed boundary solver. The effect of vortex shedding and dipole jet on the vertical force generation by the flapping wing due to change in the stroke plane angle is investigated in the vicinity of the ground. The results of instantaneous force and vorticity contours reveal the underlying lift enhancement mechanisms for the inclined stroke plane flapping wing. Moreover, they aid in the understanding of the wake-ground interaction and the associated shear layers. The calculated average vertical force delineates different force trends for the inclined stroke plane flapping near the ground. Furthermore, the dipole jet patterns are analyzed for different heights. These patterns are found to be a better tool to assess the kinematics for the vertical force enhancement and reduction, especially at intermediate heights. Vertical force enhancement is the critical parameter in the design of the micro aerial vehicle (MAV). Through this study, it is certain that the dipole jet has the potential to be used as a lift modification mechanism in MAVs. In summary, the study gives a holistic view of the physics of the inclined plane kinematics near the ground and serves as the basis for the design of MAVs.

Effect of vortex shedding on the performance of cross-flow UV-H2O2 photoreactors

In this paper, the effect of vortex shedding on the performance of cross-flow UV-H2O2 photoreactors is numerically investigated. The photoreactors are used for the degradation of two organophosphate esters, namely tributyl phosphate (TBP) and tri (2- chloroethtyl) phosphate (TCEP). An unsteady model is developed in the OpenFOAM code, which is an open-source finite volume solver. Three different photoreactors with blockage ratios of 0.55, 0.275 and 0.1375 are simulated. Parameters relevant to the unsteady behavior of the flow are calculated in each case. Also, the effect of vortex shedding on the performance of each photoreactor is investigated. It is found that the unsteadiness of the flow increases by decreasing the blockage ratio. Our results reveal that by decreasing the blockage ratio in a photoreactor, its performance increases significantly. More specifically, the photoreactor with blockage ratio of 0.1375 enhances the TBP contaminant removal by 40 percent compared to the photoreactor with blockage ratio of 0.55.

Effects of heat loads on flow and heat transfer in the entrance region of a cooling duct with a staggered array of pin fins

Computational analysis based on SAS, a hybrid RANS-LES method, were performed to study the effects of heat load on the unsteady flow and heat transfer in the entrance region of a cooling duct with a staggered array of short pin fins under conditions relevant to gas turbines. Results obtained with heat loads ranging from 3.2 to 582 kW/m2 show density and velocity variations in the boundary layers created by heat transfer to affect where separation about each pin fin takes place, the row where unsteady vortex shedding starts, the frequency of shedding, and the production of turbulent kinetic energy. It also affected the vortical structures next to the endwall in how horseshoe vortices at the base of each pin interact with the shed vortices. These heat-transfer induced changes in the flow field were found to significantly reduce the rate at which row-averaged Nusselt number, Nu¯, increases along the duct in the entrance region and to enable Nu¯ to be nearly constant in the post-entrance region even though the Reynolds number is decreasing along the duct. Results obtained also show steady RANS to under predict Nu¯ throughout the duct because it could not account for the effects of vortex shedding, and unsteady RANS to under and then over predict Nu¯ along the duct because it could not predict which row vortex shedding first starts and then over predicts its effects on heat transfer. Correlations for Nu¯ were developed that account for heat load in the entrance and in the post-entrance regions.

Experimental investigation of flame fluctuation reduction in distributed combustion

Analysis of dynamic combustor stability is essential for the development of practical devices that employ distributed reaction zones. The fluctuation of reaction zone (RZ) was studied to compare normal air combustion and distributed combustion at an equivalence ratio of 0.9 in a swirl-stabilized burner using methane fuel. Distributed combustion was fostered by diluting the inlet air stream with carbon dioxide that resulted in a gradual drop in the adiabatic flame temperature (Tad). High-speed broadband chemiluminescence at 3 kHz was used to study the global combustion dynamics. Vortex shedding observed along the shear layers influenced the oscillation of flame base in normal air combustion. However, relatively stable bases were observed in distributed combustion. Fast Fourier Transformation performed on RZ base fluctuation data supported the observations from chemiluminescence signatures. Proper orthogonal decomposition (POD) analysis indicated various vortex-shedding patterns as the dominant structures in conventional swirl flames. The power spectral density (PSD) of POD modes showed the rotational effect of RZ and weak von Karman vortex shedding to influence fluctuation in distributed combustion. The self-sustained flame oscillations in normal swirl flames were investigated from the acoustic and heat release fluctuation signals. Both acoustic and heat release fluctuations gradually reduced when approaching the distributed combustion. The PSD of these signals demonstrated a common peak at ~ 174 Hz (in normal swirl flames) with possible thermo-acoustic coupling. This peak was consistent with the peaks obtained from the base fluctuation and POD spectra. The peak gradually diminished when approaching the state of distributed combustion. A similar observation of gradually decreasing acoustic and heat release fluctuation was made with a constant Tad. However, the drop in chemiluminescence signal intensity with CO2 dilution was relatively low in case of constant Tad compared to the variable Tad case. The local and global Rayleigh index obtained for the variable Tad cases at different dilution levels showed positive values at O2 = 21 and 20%, which signified self-sustained instability. However, the distributed combustion possessed a negative Rayleigh index indicating dampening of instability. These results support the gradual decline of thermo-acoustic instability when approaching the distributed combustion condition.

Effect of aerodynamic modifications on the surface pressure patterns of buildings using proper orthogonal decomposition

This study analyzed the pressure patterns and local pressure of tall buildings with corner modifications (recessed and chamfered corner) using wind tunnel tests and proper orthogonal decomposition (POD). POD can distinguish pressure patterns by POD mode and more dominant pressure patterns can be found according to the order of POD modes. Results show that both recessed and chamfered corners effectively reduced wind-induced responses. Additionally, unique effects were observed depending on the ratio of corner modification. Tall building models with recessed corners showed fluctuations in the approaching wind flow in the first POD mode and vortex shedding effects in the second POD mode. With large corner modification, energy distribution became small in the first POD mode, which shows that the effect of the first POD mode reduced. Among building models with chamfered corners, vortex shedding effects appeared in the first POD mode, except for the model with the highest ratio of corner modifications. The POD confirmed that both recessed and chamfered corners play a role in reducing vortex shedding effects, and the normalized power spectral density peak value of modes showing vortex shedding was smaller than that of the building model with a square section. Vortex shedding effects were observed on the front corner surfaces resulting from corner modification, as with the side surface. For buildings with recessed corners, the local pressure on corner surfaces was larger than that of side surfaces. Moreover, the average wind pressure was effectively reduced to 88.42% and 92.40% in RE1 on the windward surface and CH1 on the side surface, respectively.

Energy harvesting from flow-induced vibration of a low-mass square cylinder with different incidence angles

This numerical study investigates the flow-induced vibration responses and energy harvesting characteristics of a low-mass square oscillator. We first test three typical incidence angles of α = 0°, 22.5°, and 45° with reduced velocities Ur ranging from 3.8 to 26. The most interesting phenomenon is that large-amplitude vibrations can be generated at high reduced velocities, regardless of the angle α. We show that this is because of the following mechanisms: (i) For α = 0°, galloping occurs, resulting in high-amplitude and low-frequency vibrations; (ii) for α = 45°, the cylinder undergoes vortex-induced vibrations (VIVs) without the high-amplitude galloping instability. The unsteady vortex shedding effects are enhanced by a very low mass ratio, leading to “VIV forever” in the tested range of Ur with high-level amplitudes; and (iii) for α = 22.5°, the oscillations in the high-Ur range include both VIV and galloping components. Thus, the large amplitude is caused by the galloping instability and enhanced vortex-shedding effects. Due to the existence of large-amplitude vibrations, the low-mass square cylinder demonstrates the potential and necessary robustness for energy harvesting applications. Overall, α = 45° is the most suitable arrangement for the conversion of power. To further improve the efficiency, we test a 45° cylinder under damping ratios ζ ranging from 0.01 to 0.7. The results indicate that the energy harvesting characteristics are sensitive to the damping ratio when ζ < 0.3. Of all the tested cases, ζ = 0.7 provides the highest average efficiency.

Design and Analysis of Vortex Bladeless Wind Turbine

Vortex bladeless turbine antiquates the conventional wind turbine and adopts a radically innovative and novel approach to captivate the moving wind energy. This device effectively captures the energy of vorticity, an aerodynamic instability condition. As the wind passes a structure, the flow steers and cyclical patterns of vortices are generated. Once the strength of wind force is suffice, the structure starts vibrating and reaches resonance. Vortex bladeless is a vortex induced vibration resonant power generator. It harnesses wind energy from a phenomenon of vorticity, called vortex shedding effect. Clearly bladeless technology consists of a cylinder fixed vertically on an elastic rod, instead of tower, nacelle and blades which are the crucial parts of a conventional wind turbine. The cylinder oscillates on a specifically mentioned wind range, which then generate electricity through an alternator and a tuning system. In this paper the vortex turbine is designed with certain existing parameters of dimensions in Solidworks and the same is analyzed for different materials and dimensions of mast, which is an important part in the vortex turbine. Also various performance parameters like displacement, frequency etc. are also compared among different models.

A study on the FIV hydrodynamic force coefficients of two staggered flexible cylinders via an inverse method

The flow-induced vibration (FIV) of two cylindrical structures may cause serious fatigue damage, which is a major concern in engineering fields. Few studies have focused on the FIV hydrodynamic characteristics of two staggered flexible cylinders. In this paper, the hydrodynamic coefficients of two staggered flexible cylinders are calculated using the structural responses acquired from the model tests. The cross-flow (CF) spacing ratios are set as 2, 3, 4 and 6, and the in-line (IL) spacing ratios are set as 4, 6, 8; thus, a total of twelve cases are considered. The fluctuating forces in the CF and IL directions are reconstructed using a finite element model. The forgetting factor least squares method is employed to decompose the CF/IL fluctuating force into lift/varying drag and CF/IL added mass force. In the CF direction, the hydrodynamic coefficients of the two staggered cylinders are significantly different from those of the single cylinder in the mode switch regions. The CF vibrations of the two staggered cylinders enter the higher-order mode earlier, resulting in an increase in the CF added mass coefficients. The downstream cylinder has larger lift coefficients due to the vortex shedding effect of the upstream cylinders. In the IL direction, the upstream cylinder has lower IL added mass coefficients due to the higher-order harmonics in the IL direction. The varying drag coefficients of the two staggered cylinders significantly differ from those of the single cylinder owing to the subharmonic frequency components. A hybrid aspect of wake-induced flutter and vortex-induced vibration is observed in the vibration of the downstream cylinder.

Top-Story Softening for Enhanced Mitigation of Vortex Shedding-Induced Vibrations in Wind-Excited Tuned Mass Damper Inerter-Equipped Tall Buildings

An innovative structural modification, top-story softening, is herein proposed in conjunction with an optimally tuned top-floor tuned mass damper inerter (TMDI) for improved serviceability performance in typical core-frame slender buildings with rectangular floor plan susceptible to wind-induced vortex shedding (VS) effects causing occupant discomfort. This is supported through formulating a novel optimal TMDI tuning problem in which TMDI inertial properties, i.e., attached mass and inertance, as well as the lateral top-story stiffness are design parameters aiming to minimize peak acceleration of the highest occupied floor. The optimal TMDI tuning problem is numerically solved for a wide range of design parameters for a 34-story composite core-frame building subject to stochastic spatially-correlated wind-force field accounting for VS effects. A low-order dynamical model capturing faithfully modal properties of the case-study building is developed to facilitate computational work and parametric investigation. It is found that top-story softening reduces attached TMDI mass/weight requirements and inerter force for fixed performance and inertance. It further reduces TMDI stroke and achieves increased robustness to TMDI stiffness and damping properties as well as to the assumed inherent structural damping. It is concluded that by leveraging inertance and top-story stiffness, the proposed solution can efficiently control VS-induced floor acceleration with small additional gravitational (added weight) and horizontal (inerter and damping) forces.

A wind load design method for ground-mounted multi-row solar arrays based on a compilation of wind tunnel experiments

This paper presents a concise method for determining the design wind loads for multi-row ground-mounted solar arrays, including both static and dynamic wind load coefficients compatible with the ASCE 7, based on a compilation of wind tunnel experiments conducted by RWDI using rigid pressure models. The proposed method addresses the well-established shortcomings of the ASCE 7–16 definition of ‘rigid structure’ based on the frequency of 1 ​Hz when applied to such arrays and the need identified in SEAOC PV2 (2017) that ground-mounted arrays with numerous repetitive structures shall consider vortex shedding and consequent dynamic resonant effects. Comparisons to other sources available in the technical literature have been made where possible, which are largely satisfactory, and an illustrative example is provided to assist practitioners in applying the proposed method. It is important to note that the method and data presented in this paper assume that wind-induced deflections are small, and thus, the structure is not flexible; flexible structures such as unrestrained single-axis trackers are also prone to aeroelastic effects and torsional instabilities, which are beyond the scope of this paper. Sources of uncertainty are discussed and, in an effort to minimize these uncertainties when predicting design wind loads, it is the authors’ hope that the dataset presented herein be augmented by other contributors to form the basis for codification.

The Effect of Vortex Shedding in Film-Cooling Processes

Film cooling using coolant jets is effective for increasing the cooling effectiveness of turbines. In the present study, large eddy simulation was employed for predicting small-scale vortices in the film-cooling process with different blowing ratios (BRs). The counter-rotating vortex pair (CRVP) was compared with the hairpin vortex, and results indicated the CRVP was the cross section of hairpin vortex. The results of a spectral analysis indicated a high correlation between the shedding period of the CRVP and the film-cooling effectiveness, and the dominant frequencies of the temperature and vorticity spectra were both identical to the shedding frequency of the CRVP when BR is less than 0.75. Furthermore, a higher shedding frequency of CRVP will suck the hot cross-flow into the core region more frequently, which will lead to a worse film-cooling effectiveness.

Numerical investigations on drag reduction of a civil light helicopter fuselage

The paper presents the numerical investigations for a light civil helicopter fuselage with the purpose of reducing the helicopter drag. Two numerical methods: Reynolds-Averaged Navier-Stokes (RANS) and a hybrid RANS-LES method: improved delayed detached-eddy simulation (IDDES) method are performed for the simulation of a prototype helicopter fuselage. The RANS method is validated by a modular helicopter fuselage with experimental data, while the IDDES method has already been used in other studies and good results have been achieved. The numerical results of the civil helicopter in terms of the aerodynamic coefficients obtained by the two methods are consistent with each other. Compared to the RANS method, the IDDES approach is capable of predicting the large separation flow of the fuselage/components and the small-scale vortices in the flow field. It is found that the hybrid method captures the periodically detached separating vortices behind the skid struts, while the flow at the same position simulated by the RANS method is still attached. Moreover, separating vortices, which develop diagonally upwards, are captured at fuselage/tail-boom junction by the hybrid method, whereas RANS simulation doesn't predict. Subsequently, the design of the helicopter drag reduction is carried out at α=0 deg angle of attack and 0.2 Mach number through shape optimization based on the numerical simulations, and the numerical results are verified by the force tests. It shows that the optimization of the landing skids aims at reducing the strong Karman vortex shedding effect induced by the skids, which greatly decreases the total drag. Combined with the optimization of the fuselage/tail-boom transition, this approach suppresses the separation flow of the fuselage and reduces the pressure drag, and the adjustment of transition slope benefits of up to 1.18% drag reduction, while the extension of transition reduces the drag by 2.64%. The optimization of tail-boom layout demonstrates that lower tail-boom layout can contribute to a drag reduction by 4.37% (RANS) and 3.89% (test), respectively, when compared to the original tail-boom layout.

A numerical performance analysis of a ducted, high-solidity tidal turbine

Abstract This study puts forward an investigation into the hydrodynamic performance concerning a ducted, high-solidity tidal turbine utilising blade-resolved computational fluid dynamics. The model achieves similarity values of over 0.96 with experimentation data regarding a three-bladed horizontal-axis tidal turbine in validation of three distinct parameters: power & torque coefficient, thrust coefficient, and wake velocity profiles. Accordingly, the model was employed for the analysis of a ducted, high-solidity turbine in axially-aligned flows at distinct free-stream velocities. The resultant hydrodynamic performance characteristics portrayed a peak power coefficient of 0.34, with a thrust coefficient of 0.97, at a nominal tip-speed ratio of 1.75. Coefficient trend agreement was attained between the numerical model and experimentation data established in literature and blade-element momentum theory; the model furthers the analysis by elaborating the temporal hydrodynamic features induced by the fluid-structure interaction in specification to the wake formation velocity profiles, pressure distribution along the blades and duct, mass flow rate, and vortex shedding effects to establish the characteristic flow physics of the tidal turbine.

Numerical Simulation on Vortex Shedding from a Hydrofoil in Steady Flow

This paper presents a numerical modeling procedure for the idealization of vortex shedding effects in the wake flow field of a NACA0009 hydrofoil. During the simulation, the lift and drag acting on the hydrofoil were monitored, and the vortex-shedding frequency of the hydrofoil was analyzed. The effects of inflow velocity, trailing-edge thickness, angle of attack, and maximum hydrofoil thickness on vortex shedding were investigated. The results indicate that an increase in the inflow velocity led to an increase in the vortex-shedding frequency and a negligible change in the Strouhal number. Furthermore, as the thickness of the trailing edge increased, the vortex-shedding frequency decreased gradually, whereas the Strouhal number first increased and then decreased. Vortex shedding and lift curve oscillations ceased altogether after the angle of attack of the hydrofoil increased beyond a certain threshold. When the maximum hydrofoil thickness was increased while keeping the thickness and chord length of the trailing edge constant, the vortex-shedding frequency decreased.

Numerical Investigation on Heat Transfer and Flow Characteristics of a Confined Circular Cylinder With Slit

Abstract Heat transfer and flow characteristics of channel-bounded circular cylinder with a slit vent parallel to the flow direction are numerically investigated using openfoam. The interesting feature of this configuration is the formation of the separation bubble behind the cylinder, which significantly alters the near wake characteristics. In this study, the emphasis is given to understand the effect of the slit on forced convection from the cylinder. Simulations were performed by varying the slit width from 0 to 0.25 (in steps of 0.05) for the range of Reynolds number (Re) 60–240. Re is defined based on the diameter of the cylinder (d) and centerline velocity (Uc) at the inlet of the channel. The influence of s/d and Re on the separation bubble, aerodynamic forces, and heat transfer characteristics are studied in detail. Results demonstrate that the slit can manipulate the flow to mitigate adverse effects of vortex shedding and thus can be used as a passive flow control technique. It was observed that the inclusion of the slit in the cylinder delays the onset of vortex shedding, and it also reduces the fluctuations in aerodynamic forces up to 99%. Compared with the solid cylinder, around 38% increase in vortex shedding frequency, a 16% reduction in drag, and a 10% increase in average Nusselt number is observed when the slit width is 0.25d. It was found that the introduction of slit vent in the cylinder not only enhances the heat transfer along with the reduction in expenditure of pressure loss across the cylinder but also suppresses the fluctuations in aerodynamic forces, which causes vortex-induced vibrations and thus improves structural stability and integrity.

Prediction of Scour Depth in a Group of Piers in Staggered Arrangement Using Experimental and Regression Models

The paper presents the results of a controlled experimental study to investigate the effect of mutual interference of the bridge piers placed in a staggered arrangement on local scour depth. Experiments were conducted in a standard recirculating tilting bed water flume 12 m long, 0.60 m wide, and 0.70 m deep. The size of the pier models used was 62 mm and 42 mm. For the mobile bed experiments, the uniform-sized river sand used had an average mean size, d50 = 0.23 mm and 0.30 mm. Estimation of the scour depth of the staggered arrangement of the group of piers with a constant angle of attack of 45° but varying radial pier spacing had been achieved using 54 laboratory datasets. The results of the experimental studies were compared with artificial neural network functions and random forest model analysis. From experimental results, it is found that the downstream piers were placed at a radial spacing greater than five times the diameter of the bridge pier; the vortex shedding effect produced by the front pier on the rear piers is negligible.

Optimal tuned mass-damper-inerter (TMDI) design in wind-excited tall buildings for occupants’ comfort serviceability performance and energy harvesting

The tuned mass-damper-inerter (TMDI) couples the classical tuned mass-damper (TMD) with an inerter device which develops a resisting force proportional to the relative acceleration of its ends by the “inertance” constant. Previous works demonstrated that the TMDI leads to efficient broadband vibration control for a range of different structures under different dynamic excitations. This paper proposes a novel optimal TMDI design formulation to address occupants’ comfort in wind-excited slender tall buildings susceptible to vortex shedding (VS) effects and to explore optimal TMDI’s potential for transforming part of the wind-induced kinetic energy to usable electricity in tall buildings. Attention is focused on investigating benefits of TMDIs with different inertial properties (i.e., secondary mass/weight and inertance) configured in different topologies defined by the number of floors spanned by the inerter device to connect the secondary mass to the building structure. Optimally designed TMDIs for a wide range of inertial properties and three different topologies are obtained through numerical solution of the underlying optimization problem for a benchmark 305.9 m tall building with more than 6 height-to-width ratio subjected to experimentally calibrated spatially-correlated across-wind force field accounting for VS effects. Fixed performance design graphs on the TMDI inertial (mass-inertance) plane are furnished demonstrating that any fixed structural performance level in terms of occupants’ comfort (i.e., peak top floor acceleration) can be achieved through lightweight TMDIs as long as sufficient inertance is provided. Further, TMDI robustness to host structure properties and to reference wind velocity is shown to increase by increasing inertance or by spanning more floors in connecting the secondary mass with the host structure by the inerter. Lastly, it is found that increased available energy for harvesting in wind excited tall buildings is achieved by incorporating electromagnetic motors in TMDIs with varying damping property, while concurrent reduced floor acceleration and increased available energy for harvesting is accomplished by TMDI topologies with inerters spanning more floors.

Modeling of net sediment transport rate due to wave-driven oscillatory flow over vortex ripples

A one-dimensional-vertical (1-DV) model is developed for predicting net ripple-averaged sediment transport rate over a rippled bed under wave-driven oscillatory boundary layer flows. This model is extended from a sheet-flow model developed by Yuan and Tan [52], which is able to account for the effect of wave nonlinearity (velocity skewness and asymmetry) together with a mild bottom slope. The rippled bed is conceptualized as a flat bed with a large bottom roughness accounting for the presence of ripples in modeling the boundary layer flow and sediment concentration. The vortex-shedding effect is incorporated into the model by adding a pick-up rate on top of the one induced by skin-friction turbulence. The model performance is good for 2-D ripples under periodic oscillatory flows, which are used for calibrating the model. We also showed that it is applicable for 3-D ripples and irregular oscillatory flows. In addition, this 1-DV model can capture some intermediate ripple- and period-averaged physical processes, e.g., cycle averages of velocity, sediment concentration and sediment flux, suggesting that the model correctly captures the underlying physics. The relative importance of vortex-shedding effect is shown to be controlled by ripple dimension, sediment grain size and the driving mechanisms for net sediment transport rates.