Velocity Vorticity Research Articles

Flow instability and vortex evolution in a three-twisted-blade pump using delayed detached eddy simulation

The study investigates the fluid dynamics and instability mechanisms of a three-twisted-blade pump using hydrodynamic field analysis, vortex identification, and spectral methods. High-fidelity numerical modeling was conducted with OpenFOAM, employing the Delayed Detached Eddy Simulation method and an arbitrary mesh interface on structured grids. The results identify two distinct fluid motion mechanisms: in the flow passage range of R45%–R60%, significant velocity fluctuations and vortex shedding lead to turbulent flow, while in the R80%–R90% range, the flow becomes more stable with weaker fluctuations. Vortex motion in the flow passages, driven by the twisted blade shape, resembles the Kármán vortex street. On the suction side of the blade leading edge, striped vorticity patterns extend and densify with increased flow rate and rotational speed, correlating with the vortex shedding frequency. An increased flow rate promotes the transition from single-axis to multi-axis frequency in the velocity Power Spectral Density (PSD), counteracting the volute tongue effect and eliminating single-blade frequency. Conversely, higher rotational speeds intensify turbulence near the blade tip but minimally affect the velocity PSD's peak frequency domain.

Observations of the Electromagnetic Electron Kelvin‐Helmholtz Instability and Its Impact on the Dynamics Inside a Flux Rope

AbstractThe electromagnetic electron Kelvin‐Helmholtz instability (EM EKHI) and its impact on the dynamics inside a flux rope (FR) is investigated through observations from the Magnetospheric Multiscale mission. The convection term dominated electric field drives E × B drift in the FR, which supports a strong electron shear flow. The electron shear flow is unstable to the EM EKHI, which results in an electron velocity vortex and many current filaments in the FR. In one of the current filaments, ion and electron demagnetization and strong energy conversion are observed. The continuous radial nulls and obvious reconstructed X‐line topology indicate that magnetic reconnection may occur in this current filament.

Investigation of the steady regimes in a cross-shaped reactor by particle image velocimetry

In the chemical engineering area, impinging flow plays a significant role in process intensification and energy consumption reduction. Thoroughly revealing the formation and evolution of vortices within the reactor has emerged as a crucial scientific issue. This paper systematically studies the steady-state flow at low Re (1 ≤ Re ≤ 200, where Re is the Reynolds number) in a cross-shaped reactor by particle image velocimetry technology. The evolution, distribution, and intensity characteristics of vortices in the reactor chamber are focused on. We show that at 55 ≤ Re ≤ 120, the distribution of vorticity and shear rate in the chamber show unimodal and bimodal patterns, respectively, and the center of the chamber is a local area with high vorticity and low shear. In contrast, for 120 < Re ≤ 200, the distribution of vorticity turns into a bimodal pattern, and the shear rate develops into a trimodal pattern. The center of the chamber constitutes a local area characterized by low vorticity and high shear. Additionally, based on the modified monopole vortex model, the distributions of vorticity and velocity of vortices in the steady engulfment flow are accurately depicted.

Computational and experimental analysis of flow velocity and complex vortex formation around a group of bridge piers

Computational and experimental analysis of flow velocity and complex vortex formation around a group of bridge piers

CFD-Based Investigation of the Operation Process of Radial Labyrinth Machinery Under Different Geometrical Configurations

This study explores the performance and flow characteristics of radial labyrinth pumps (RLPs) under various geometrical configurations and operating conditions. Experimental investigations and numerical simulations were conducted to evaluate the impact of design parameters such as blade geometry, channel width and blade angle on pump hydraulic performance. The numerical model, developed using the realizable k-ε turbulence model, was validated with experimental data, achieving satisfactory convergence (4.8%—bladed active disc operating with a smooth passive disc and 3.0%—bladed active disc operating with a bladed passive disc). Analysis of the velocity profiles and vortex structures formed between the active and passive discs was performed. These findings underscore the importance of optimizing disc geometry to balance centrifugal effects and momentum exchange. The obtained head for the model with a bladed active disc operating with a smooth passive disc was H = 24.1 m, while, for the bladed active disc operating with a bladed passive disc, it was almost 1.7 times higher at H = 40.3 m. Additionally, the research identifies potential zones within the pump where energy transfer processes differ, providing insight into targeted design improvements. The findings provide valuable information on the optimization of RLP designs and their broader applicability.

On the river flow motion in the bend channel cross-section

At the river bed curves, secondary flow normal to the main flow direction are formed. Depending on the channel geometry, there may be several secondary flows in the cross-section, and they may have different scales. Even a small secondary cross-section flow affects the parameters of the hydrodynamic flow and this influence must be taken into account when modeling riverbed processes and researching coast deformations of the channel. Three-dimensional modeling of such multi-scale processes requires large computational costs and is currently possible only for small model channels. Therefore, a reduced-dimensional model is proposed in this paper to study coastal processes. The performed reduction of the problem from a three-dimensional model of river flow motion to a two-dimensional one in the plane of the channel cross-section assumes that the hydrodynamic flow is quasi-stationary and the hypotheses on the asymptotic behavior of the flow along the flow coordinate are fulfilled for it. Taking into account these limitations, a mathematical model of the problem of a stationary turbulent calm river flow in a channel cross-section is formulated in this work. The problem is formulated in a mixed velocity–vortex–stream function formulation. Specifying of the boundary conditions on the flow free surface for the velocity field determined in the normal and tangential directions to the cross-section axis is required as additional conditions for the problem reduction. It is assumed that the values of this velocity field should be determined from the solution of auxiliary problems or obtained from data of natural or experimental measurements. The finite element method in the Petrov–Galerkin formulation is used for the numerical solution of the formulated problem. A discrete analog of the problem is obtained and an algorithm for its solution is proposed. The performed numerical studies showed generally good agreement between the obtained solutions and the known experimental data. The authors associate the errors in the numerical results with the need for a more accurate determination of the radial component of the velocity field in the cross-section by selecting and calibrating a more suitable model for turbulent viscosity calculating and a more accurate determination of the boundary conditions on the cross-section free boundary.

Differentiated Impacts of Central and Eastern Atlantic Niño on Hurricane Activity in the Tropical North Atlantic

AbstractRecent research highlights the influence of the Atlantic Niño on the likelihood of strong hurricanes forming in the tropical Atlantic. This phenomenon increases the risk of hurricanes impacting the Caribbean islands and the United States. A recent study identifies two distinct types of the Atlantic Niño, with warming concentrated in the central (CA) and eastern (EA) equatorial Atlantic, respectively. By analyzing observational and reanalysis data, we investigated how these two types of the Atlantic Niño affect hurricane activity. The findings reveal that the CA Niño enhances hurricane frequency south of 20°N, while the CA Niña promotes hurricanes north of 20°N. The CA Niño exerts a more significant influence on hurricanes than the EA Niño, primarily by affecting wind shear, relative vorticity, and vertical velocity. In contrast, the EA Niño mainly impacts relative humidity and African Easterly Waves. These insights could improve the accuracy of seasonal hurricane forecasts.

Implementation of the spectral element discretization of the nonstationary velocity–vorticity–pressure Stokes formulation

This paper deals with the resolution of the time-dependent velocity–vorticity–pressure formulation of Stokes problem in a two- and three-dimensional domain. The discretization is based on the spectral element method with respect to the space variable and Euler’s implicit scheme with respect to the time variable. We implement the asymmetric linear system to solve the full spectral element discrete problem. Detailed numerical experiments lead to confirm the usefulness of the discretization.

Turbulent plasma flow, its energies, and structures: Velocity vortices, magnetic field cocoons, and plasmoids

Context. Turbulent flows are believed to be present in the solar corona, especially in connection with solar flares and coronal mass ejections. They are supposed to be very effective processes in energy transportation and can contribute to the heating of the solar corona. Aims. We study turbulence in reconnection outflows associated with flares and coronal mass ejections. We simulated the generation and evolution of the turbulent plasma flow and investigated its energies and formed plasma velocity and magnetic field structures. Methods. For the numerical simulations, we adopted a three-dimensional (3D) magnetohydrodynamic (MHD) model, in which we solved a full set of the 3D time-dependent resistive and compressible MHD equations using the LARE3D numerical code. Results. We numerically studied turbulence in the plasma flow in the model with the plasma parameters that could simulate processes in the magnetic reconnection outflows in solar flares. Starting from a non-turbulent plasma flow in the energetically closed system, we studied the evolution of the kinetic, internal, and magnetic energies during the turbulence generation. We found that most of the kinetic energy is transformed into the plasma heating (about 95%) and only a small part to the magnetic energy (about 5%). The turbulence in the system evolves to the saturation stage with the power-law index of the kinetic density spectrum, −5/3. Magnetic energy is also saturated due to its dissipation and reconnection in small and complex magnetic field structures. We show examples of the structures formed in studied turbulent flow: velocity vortices, magnetic field cocoons, and plasmoids.

CFD Investigation of Mechanical Heart Valve Orientations in Modulating Left Ventricular Hemodynamics

This study provides a comprehensive computational analysis of how mechanical heart valve orientations impact left ventricular (LV) hemodynamics, with potential implications for surgical valve placement. Focusing on monoleaflet valves (MLV) and bileaflet valves (BLV), the research explores how different valve angles influence blood flow patterns within the LV chamber. The analysis includes velocity contours, streamline patterns, vorticity contours, and temporal velocity fluctuations to elucidate the effects of valve orientation on LV performance. Findings indicate that valve orientation significantly influences flow coherence and blood velocity. For instance, a 20-degree orientation in the MLV alters jet flow in ways that could affect wall shear stress distribution. At a 45-degree angle, the MLV produces a more centralized jet flow, enhancing flow uniformity and aligning more closely with physiological conditions. In contrast, a 55-degree angle skews the jet flow, potentially leading to adverse hemodynamic effects. Similarly, BLV orientations at 45, 55, 60, and 70 degrees showed that lower angles improved flow efficiency, reducing energy losses and minimizing the risk of regurgitation, while higher angles led to turbulent and potentially damaging flow patterns. Comparative results at a 45-degree orientation demonstrated the superior performance of BLV in regulating normal velocity, with BLV reducing average blood velocity by 38.77% compared to a 29.53% reduction with MLV. These results underscore the importance of optimizing mechanical heart valve orientations to enhance left ventricular hemodynamics. The findings carry significant clinical implications, supporting evidence-based valve placement decisions that can substantially improve patient outcomes, survival rates and long-term cardiovascular health.

PH, pOH shift and electroconvection of strong and weak electrolytes under ion concentration polarization

Ion concentration polarization (ICP) phenomenon near permselective membranes and associated electroconvection contributes greatly to ion enrichment, desalination, and biomolecular separation. Despite extensive studies on ion transport and fluid dynamics near the ion exchange membrane (IEM) surface, the influence of hydrolysis and buffer reactions on pH changes and electroconvection remains unclear. This study investigates the pH variations and electroconvection changes in different electrolytes under ICP, through numerical simulations in strong (NaCl) and weak electrolytes (Na2HPO4). Our findings reveal that the free ions produced by reactions increase the electrical conductivity, significantly boosting the current by approximately 14.82% in weak electrolyte in the overlimiting current (OLC) regime. The vortex velocity generated by electroconvective instability also increases by two times at the threshold voltage of 23 times the thermal voltage (25.8 mV). Additionally, the decrease in ion concentration during the ICP causes a significant pH and pOH surge in the quasi-equilibrium electric double layer (QE-EDL) and extended space charge (ESC) region, causing the water self-ionization constant (pKw) to surpass 14. Hydrolysis reactions release H+, reducing the pH surge by 0.5 and raising the OH− concentration in the diffusion boundary layer (DBL) region, resulting in a pOH of 6.5, which is higher than that of the bulk solution. In Na2HPO4 solution, weak acid dissociation reactions confine pH changes to the QE-EDL and ESC regions, maintaining pH stability in the DBL region. It was also found that at the boundary of the DBL region, the disruption of electro-neutrality results in the highest dissociation reaction rates. This research highlights the interplay of buffer reactions, hydrolysis, pH changes, and electroconvection near the IEM surface, with implications for applications involving ion transport and pH control.

Structural and dynamic characteristics of horseshoe vortex systems in front of rigid vegetation inclined upstream under conditions of overland flow

Inclined angle significantly impacts horseshoe vortex (HV) system and subsequent flow events upstream of vegetation stems, which are crucial for understanding of erosion mechanisms and geodynamics. Flume experiments were conducted to investigate dynamic characteristics of horseshoe vortex (HV) system upstream of inclined rigid vegetation stems under shallow overland flow conditions. Five inclination angles (10°, 20°, 30°, 40°, 50°) were tested alongside a vertical column (0°) across four low Reynolds number conditions (ReD = 2995–4639). Using high-precision particle image velocimetry (PIV) system, we measured the flow field in upstream symmetry plane of the cylinder. Then time-averaged primary HV features were analyzed in terms of the location, radius, vorticity, swirling strength, flow direction and vertical velocity. The increasing inclination angle weakens the formation of the HV system. This is evident in the decrease of vorticity and swirling strength, as well as the gradual diffusion and eventual rupture of the HV system. In the horizontal direction, the primary HV gradually moves away from the cylinder, with minimal vertical impact. The radius of the main HV is positively correlated with the tilt angle, while vorticity and rotation intensity are negatively correlated. We also examined the time-resolved characteristics of the velocity components. The probability density functions (PDFs) of streamwise and vertical velocity components show asymmetric double peaks, indicating two high-frequency events: backflow and downwelling. Linear random estimation revealed that the backflow event is driven by a high-momentum counter current passing through the primary HV, which is mainly dominated by a backflow mode, while the downwelling event arises from low-momentum fluid that cannot penetrate the HV, dominated by a zero-flow mode. These two modes exhibited minimum and maximum time percentages within the current time range, highlighting erosion dynamics from the perspectives of flow event frequency and momentum theory.

A novel resonant mode drives the dynamics of a large-cavity synthetic jet actuator

Synthetic Jet (SJ) actuators are an intrinsically complex combination of electronics, electric and mechanical systems. When studied theoretically, these elements are often simplified to coupled damped harmonic oscillators (DHO) that induce a pressure field within the cavity and drive momentum exchange. Thus, the dynamics of an SJ actuator result from coupling these DHOs, naturally leading to a few resonant modes. There is good evidence in the specialized literature of two resonant modes developing in SJ actuators: the membrane/piezoelectric mode and the Helmholtz resonance. In this work, we report on the effect of a new resonant mode that dominates the two traditional modes when it develops. We present evidence that the resonant mode develops when the cavity is much larger than the volume displaced by the actuator. The new resonant mode is biased to lower frequencies and has a flatter response along the frequency band than other resonant modes. We show that jet and vortex velocities mimic the sound pressure curve for the low-frequency range. Its effect mitigates for the higher range due to a delve through shorter stroke lengths, characterized through the well-documented formation criteria as a fixed relation between the Reynolds and the Stokes numbers. We further characterize the new resonant mode by comparing its intensity with standard room modes. We also show that the resonant mode may be dimmed and focused by adding an obstacle in different cavity positions for the lower sound intensities. We consider that the large-cavity dynamics is an additional element that, if integrated as design criteria, could extend the applicability of SJs and their optimum response.

Investigation of geometric structure on energy performance and flow characteristics in underwater hydraulic machinery

PurposeFor underwater hydraulic machinery, the unique structure significantly enhances the three-dimensional non-uniformity of turbulence within the flow domain and high Reynolds number turbulence introduces complex effects on the machinery. Therefore, studying the turbulent flow characteristics in underwater hydraulic machinery is crucial for system stability.Design/methodology/approachThis paper conducts a numerical analysis on a specific type of underwater hydraulic machinery. A numerical calculation model is established under stable inflow conditions to analyze the flow trends and pressure changes at different flow speeds. Subsequently, structural modifications are made to the underwater hydraulic machinery, and the characteristics of the velocity field, pressure field and vorticity distribution under different model parameters are analyzed.FindingsThe results indicate that changes in internal structure have a certain impact on flow characteristics. When the structural changes are significant, the fluid flow becomes more complex and pressure fluctuations become more intense. The research findings provide a scientific basis and theoretical guidance for the structural design of underwater hydraulic machinery and have significant research implications for controlling fluid-induced noise.Originality/valueAffected by the inherent structural characteristics of the flow channel structure, the flow direction of the high-speed water flow changes drastically in the flow channel, so it is of great significance to study its flow characteristics for the stability of the system.

Fluid flow simulation with an [formula omitted]-accelerated Boundary-Domain Integral Method

The development of new numerical methods for fluid flow simulations is challenging but such tools may help to understand flow problems better. Here, the Boundary-Domain Integral Method is applied to simulate laminar fluid flow governed by a dimensionless velocity–vorticity formulation of the Navier–Stokes equation. The Reynolds number is chosen in all examples small enough to ensure laminar flow conditions. The false transient approach is utilized to improve stability.As all boundary element methods, the Boundary-Domain Integral Method has a quadratic complexity. Here, the H2-methodology is applied to obtain an almost linear complexity. This acceleration technique is not only applied to the boundary only part but more important to the domain related part of the formulation. The application of the H2-methodology does not allow to use the rigid body method to determine the singular integrals and the integral free term as done until now. It is shown how to apply the technique of Guigiani and Gigante to handle the strongly singular integrals in this application. Further, a parametric study shows the influence of the introduced approximation parameters. For this purpose the example of a lid driven cavity is utilized. The second example demonstrates the performance of the proposed method by simulating the Hagen–Poiseuille flow in a pipe. The third example considers the flow around a rigid cylinder to show the behavior of the method for an unstructured grid. All examples show that the proposed method results in an almost linear complexity as the mathematical analysis promisses.

Stability and receptivity analyses of the heated flat-plate boundary layer with variable viscosity

This article presents the modal, non-modal, and resolvent analyses of the boundary layer developed over a heated flat-plate with temperature-dependent viscosity using linear stability theory. The governing equations are derived in the normal velocity–vorticity form by imposing small infinitesimal disturbances on the base flow with the Oberbeck-Boussinesq (OB) approximation. The spectral method is employed to discretize the governing stability equations in the wall-normal direction. The base flow comes from the similarity solution using R-K4th order method along with shooting techniques. The effects of viscosity stratification, inertia, shearing, and buoyancy on the stability of the boundary layer are investigated by varying the sensitivity parameter (ϵ), Reynolds (Re), Prandtl (Pr), and Richardson numbers (Ri). The modal analysis shows the time-asymptotic behavior of the disturbances and onset of instability is mainly caused by amplification of Tollmien–Schlichting (T-S) waves similar to as observe in the traditional Blasius case. The modal stability increases with increase in sensitivity parameter and stabilizing effects become more pronounced for liquid than gas. However, the thermal effects lead to destabilize the flow and strong destabilizing effects produced for higher Prandtl number. On the other hand, non-modal analysis displays an early transient growth of disturbances and an existence of these non-normality effects identified from the pseudospectra via. resolvent analysis. The non-modal growth increases with increase in ϵ even though T-S modes shift towards the damped region, which indicates the continuous modes in the eigenspectrum are more dominated than the discrete T-S modes due to the thermal effects. To clarify this qualitative change, a component-wise input–output analysis is performed to measure the receptivity to particular external disturbances. The results show the thermal energy of the disturbances is converted into kinetic energy due to thermal effects, resulting in strong receptivity amplification at the continuous mode due to the non-normality of the linear operator. Thus, the boundary layer under the influence of viscosity stratification, heating, and shearing effects is vulnerable to free-stream disturbances that could significantly affect bypass transition

Exact planetary waves and jet streams

We investigate exact nonlinear waves on surfaces locally approximating the rotating sphere for two-dimensional inviscid incompressible flow. Our first system corresponds to a $\beta$ -plane approximation at the equator, and the second to a $\gamma$ approximation, with the latter describing flow near the poles. We find exact wave solutions in the Lagrangian reference frame that cannot be written down in closed form in the Eulerian reference frame. The wave particle trajectories, contours of potential vorticity and Lagrangian mean velocity take relatively simple forms. The waves possess a non-trivial Lagrangian mean flow that depends on the amplitude of the waves and on a particle label that characterizes values of constant potential vorticity. The mean flow arises due to potential vorticity conservation on fluid particles. Solutions over the entire space are generated by assuming that the flow far from the origin is zonal and there is a region of uniform potential vorticity between this zonal flow and the waves. In the $\gamma$ approximation, a class of waves is found that, based on analogous solutions on the plane, we call Ptolemaic vortex waves. The mean flow of some of these waves, which we can describe in highly nonlinear scenarios due to the exact nature of the solutions, resembles polar jet streams. Several illustrative solutions are used as initial conditions in the fully spherical rotating Navier–Stokes equations, where integration is performed via the numerical scheme presented in Salmon & Pizzo (Atmosphere, vol. 14, issue 4, 2023, 747). The potential vorticity contours found from these numerical experiments vary between stable permanent progressive form and fully turbulent flows generated by wave breaking.

Hydrodynamic parameters affecting flow-accelerated corrosion in elbows

Flow-accelerated corrosion (FAC) is a serious degradation mechanism affecting carbon-steel piping in the secondary coolant systems of nuclear power plants. Many researchers have investigated the correlation between wall thinning and hydrodynamic parameters; however, their relationship remains unclear. In this study, the hydrodynamic parameters influencing FAC in elbow sections were investigated for identifying the locations highly susceptible to FAC. Accelerated FAC tests and computational fluid dynamics (CFD) analyses were conducted on a specimen containing elbow sections. The results revealed that the side of the elbow pipe was the most susceptible to FAC because it experienced the most severe wall thinning. The velocity and vorticity vectors obtained from the CFD analysis were decomposed into axial, circumferential, and radial components within a cylindrical coordinate system to evaluate their effects. We found that all velocity and vorticity components contribute to the rate of wall thinning induced by FAC. Therefore, a combination of velocity and vorticity components should be used as hydrodynamic parameters to characterize FAC-induced wall thinning. Specifically, the circumferential velocity and axial vorticity were identified as dominant parameters influencing FAC in the elbows.

Unsteady flow analysis in a pump as turbine impeller based on proper orthogonal decomposition and dynamic mode decomposition methods

Pump as turbine (PAT) is an efficient, simple, and cost-effective equipment combining pump and turbine and is one of the excellent energy recovery devices. It is helpful to master the flow characteristics of the key component impeller for the further optimization and design of the PAT. To analyze the unsteady flow features in the impeller of a double-suction pump operating as a turbine, numerical simulations were conducted using the shear stress transport (SST) k-ω turbulence model at the designed operating conditions. By utilizing proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods on the unsteady velocity field of a single cycle, the dominant modes up to the fourth order, along with their respective space–time information, can be extracted. The velocity field and vorticity field analysis were performed on the first four modes extracted using two different methods. Additionally, the vortex structures were extracted using the Ω method. The analysis demonstrates that the POD and DMD methods effectively decompose the intricate flow characteristics within the impeller into dynamic–static interference modes, fundamental modes, and dissipative modes. The dynamic–static interference mode is dominant, reflecting the flow characteristics influenced by the stationary components within the impeller. The vortex structure is mainly small tubular vortex and point vortex. The fundamental mode captures the steady flow field characteristics caused by the blade channel geometry. The vortex structure is mainly continuous tubular vortex and the diameter becomes larger. The dissipative mode reflects the flow separation generated on the blades by disturbances from the stationary components. The vortex structure is dominated by point vortex and discontinuous tubular vortex. Comparing the outcomes of the two modal analysis methods shows that the POD method has a distinct advantage in showcasing key changing nodes. In contrast, the DMD method is superior in isolating modes with a single frequency and in determining their stability.

Numerical study of transition hydraulic jumps in different types of stilling basins using lattice Boltzmann methods

Transition hydraulic jumps, also known as low-Froude number jumps, have been less studied compared to high Froude number jumps, despite their significance in high-discharge and low-head dams. A three-dimensional (3D) Lattice Boltzmann method simulation was conducted to investigate submerged transition hydraulic jumps in both normal and expanded stilling basins, focusing on turbulent flow characteristics such as velocity fields, vorticity features, pressure fluctuations, and coherent structures. In expanded basins, two symmetric separated rollers were observed, with the rollers detaching from the submerged jump as the width of basin increased. The length of submerged roller in normal basins is observed as Lr/Ht = 6.19, while it is decreased to Lr/Ht = 4 in expanded basins because of the occurrence of roller lateral diffusion toward sidewalls. The transition of vortex structures from y- to z-vortical was analyzed, and three-dimensional shear layers are captured using the iso-surface of vorticity magnitude ω = 6.5. To further describe the internal structure of turbulence within the transition hydraulic jump, the coherent flow structures are qualitatively examined using the Ω criterion that is the third generation of vortex identification technique. Pressure fluctuations in low-Froude number stilling basins, described using root mean square (RMS), are first presented. High patches of RMS are found in the flow fields and at the bottom of basins, and it is qualitatively noted that shear effects make great contributions to the pressure fluctuations. Distribution of bottom pressure fluctuation RMS in different types of basin was also analyzed. The peak RMS value occurs at the ogee region of the weir, specifically at x/L = −0.2, and it is mainly affected by the width of expansion. Bottom pressure fluctuation RMS decreases in the following order: Normal, 5 m gradual expansion, 10 m gradual expansion, 5 m sudden expansion, and 10 m sudden expansion, due to the lateral diffusion of rollers toward sidewalls. This research introduces an innovative numerical simulation approach to studying pressure fluctuations, offering valuable insights for hydraulic engineering applications.