Water Depth Ratio Research Articles

Investigation of Sloshing with Vertical and Horizontal Baffle in the Prismatic Tank using Meshfree CFD

Sloshing is a phenomenon where the tank experiences an external oscillating motion due to the interaction of fluid with tank. The most appropriate way to prevent instability from the sloshing movement is to add baffles or anti-sloshing. This paper was conducted with the 3D simulation of sloshing roll motion on the prismatic tank with a simulation time of 28 seconds. Vertical and Horizontal baffles were used to mitigate sloshing in the prismatic tank. The ratio of baffle height and water depth is 0.7, 0.8 and 0.9. Moreover, horizontal baffle position is 0.1, 0.2, 0.3, and 0.4 respectively, with the tank filling water ratio is 25%. The numerical study was carried out using meshfree CFD, i.e., Smoothed Particle Hydrodynamics. In addition, advanced post-processing was conducted with Blender. The aims of this study were found out the effective baffle configuration ​​to reduce sloshing using vertical and horizontal in the prismatic tank. The results showed the most effective baffle variation for roll motion is 0.9 for vertical baffle and a horizontal baffle height is 0.1 from the water surface. It showed baffles effectively reduces dynamic pressure, hydrodynamic force and free surface deformation

2D and 3D numerical simulations of dam-break flow problem with RANS, DES, and LES

In this study, dam-break flows occurring on different downstream/upstream water depth ratios (α = 0, 0.1, and 0.4) and different obstacle shapes are numerically modeled in 2D and 3D. The Finite Volume Method (FVM) is used in the numerical solution of the basic equations governing the propagation wave formed as a result of the dam-break, and the interface of water with air is calculated by the Volume of Fluid (VOF) method. In modeling turbulence stresses, four turbulence models particularly successful in curvilinear trajectories and high strain flows, namely the Re-normalization Group (RNG), Shear Stress Model (SST), Detached Eddy Simulation (DES), are employed for the 2D simulation, and Large Eddy Simulation (LES) for the 3D simulation. The numerical results are compared against the previous experimental results and the performance of the turbulence models is evaluated according to the Mean Absolute Relative Error (MARE) criteria. For the 2D analysis, it has been determined that the DES is more successful for α = 0, 0.1, and 0.4, whereas the SST is more successful for triangular and trapezoidal obstacles in the downstream region than other turbulence models. Comparing the 2D and 3D results, the 3D LES model is expected to be more compatible with the experimental water surface profiles for all conditions among the models used in the study. It has been concluded that turbulence models, in which the strain tensor is considered, are successful in modeling the propagation wave formed as a result of a dam-break.

Effects of Secondary Current on the Local Erosion Induced by Circular Turbulent Wall Jets in Cross Flow

This paper presents the results of a series of laboratory experiments, by placing a turbulent wall jet in the upstream and downstream of a 90° channel bend, to investigate the effects of secondary flow on formation of local sediment erosion and deposition. The effects of jet and current flow intensities on the erosion pattern were characterized by the jet’s Reynolds number, Re, channel Froude number, Fr, and the ratio of water depth to nozzle diameter, h/do. The geometrical characteristics of local erosion such as jet trajectory, maximum scour depth, ds, and maximum mound height, hm, were measured. The area and volume of scours and mounds were calculated from measurements, and the results were correlated with the controlling parameters. Experimental observations indicated the existence of distinct scour patterns due to variations of channel Froude number. Two additional scour holes were identified due to the effect of stream interactions and formation of vortex regions immediately downstream of sediment mound. It was found that both channel and jet flows contributed to trajectory of the jet and the footprint of erosion. A threshold Froude number of Fr=0.091 was identified at which the current and jet flow were in equilibrium. The results showed that for a constant value of Fr, all scour parameters increased with increasing Reynolds number. However, Re did not have any effects on the jet’s deflection. Comparing the erosion profiles in the upstream and downstream bend indicated that the secondary current and turbulent redistribution altered the erosion and mound formation in the downstream of the bend in relatively high Reynolds (i.e., Re≥23,000), high channel Froude numbers (i.e., Fr>0.091) and high jet submergence (i.e., h/do>10.53).

Analysis of the kinetic energy recovery behind a tidal stream turbine for various submergence levels

Tidal turbines are commonly deployed at sea sites with water depths of up to 50 m to ease their deployment and quick maintenance operations. In these relatively shallow water depth conditions, the vertical expansion of tidal stream turbine wakes is restricted by the proximity of the rotor blades to the bottom bed and free-surface layer. These physical constrains can lead to changes in the flow mechanisms that drive momentum recovery behind the turbines, e.g. limiting the vertical fluxes of velocity. Understanding how the wake recovers depending on the submergence ratio is of utmost importance to designing the future multi-row tidal turbine arrays. Here, we adopt high-fidelity Large-Eddy Simulations (LES) with an Actuator Line Method (ALM) to represent the turbine's rotor to analyse the mean flow and transport equation for mean kinetic energy (MKE) behind a single bottom-fixed tidal turbine for four water depth values. Our results show that the close proximity of the turbine blade tip to the free-surface can notably constrain the wake expansion, with very shallow conditions leading to a limited contribution to the MKE replenishment of the turbulent momentum exchange over the vertical direction. Conversely, under such shallow conditions, the horizontal flux of MKE is enhanced over the lateral boundaries of the downstream wake. Our study evidences that the ratio of water depth to turbine diameter plays a relevant role in future tidal arrays and needs to be correctly accounted for in numerical models to provide reliable results.

Solitary wave interaction with upright thin porous barriers

The interaction of fluid flow with porous barriers has numerous practical applications, including as a partial barrier to water waves that damp some of the approaching energy at the same time as allowing environmental flow. However, surprisingly little effort has been expended on understanding the fundamentals of this interaction. Therefore, this study aims to model the interaction between waves and thin, upright porous barriers. This is undertaken by modelling the porous barrier empirically within a Smoothed Particle Hydrodynamics (SPH) framework that is then used to model wave flume experiments. Although detailed modelling of the interaction is possible at the laboratory scale, it is not feasible in practical settings where a barrier will contain many thousands of holes that cannot be individually modelled. The key information needed to model the barrier empirically is obtained from solitary wave-porous barrier interaction experiments. Our results indicate that, for each barrier, irrespective of the properties of the wave interacting with it, there is a coefficient value that is able to account adequately for the energy dissipation by the barrier. The reliability of the approach has been demonstrated by comparing SPH model predictions against companion sinusoidal wave-porous barrier experimental measurements. The SPH model was then used to determine the energy dissipation characteristics of porous barriers kept at different draught to water depth ratio, D/d, without reference to the wave flume experiments. Simulation results indicate that barriers are more effective in dissipating the incident wave energy if its draught is over 75% of the water depth.

Investigation of the interaction of internal solitary waves with the slope-shelf topography

In this paper, internal solitary waves (ISWs) propagating over shelf topographies are studied based on numerical experiments conducted according to the lock-release method. The wave generation, propagation, and interactions with slope-shelf topography are investigated in a wave tank. The primary features of the propagation of ISWs on the slope are assessed. Shear and advection instabilities are observed in the current simulations in some cases with 1.29 < Bs < 1.75 (Bs is defined as the ratio of layer water depth on the shelf to the ISW amplitude). The induced density flow contributes to the growth of potential energy by dilution and stripping, primarily through its head, which is one of the factors used to enhance the mixing efficiency. In addition, the obtained results are compared with those of previous experiments conducted by other researchers, while considering the differences in local topography. The comparison reveals that local topography is a reason for the experimental differences of some research studies. ISW breaking on a slope is strongly influenced by the initial flow field of the slope, which may lead to differences in the prediction of the breaking point by using boundary layer separation as a criterion. As the incident wave amplitude increases, the location of the breaking point shifts downward and its magnitude gradually decreases.

The combined refraction–diffraction effect on water wave scattering by a vertical flexible–porous structure

This article investigates the combined effect of refraction–diffraction due to bottom topography on water wave scattering by a vertical flexible–porous structure. This model problem assumes two partial configurations of the structure, such as surface-piercing and bottom-standing positions. Wave scattering is studied under the assumptions of small amplitude water wave theory and Darcy law for flow through the porous medium. The solution method uses Eigenfunction expansion of velocity potentials in the uniform bottom region and the Galerkin-Eigenfunction expansion in the variable bottom region. The structure deflection is obtained by Green’s function technique. From the porous boundary condition, a Fredholm integral equation with Green’s function as the kernel is derived, and its solution is approximated by Galerkin expansion. The associated boundary value problem is converted to a system of algebraic equations. The variations of reflection and transmission coefficients of incident waves are illustrated with parameters related to waves and flexible structure. The flexible structure effect on Bragg resonance is explored in the case of a rippled bottom. Furthermore, the effect of depth ratio on wave scattering is studied in the case of a sloping plane step-type bottom. Some striking results are derived from this model. Bragg resonance reduces with increasing thickness of flexible structure and friction of porous medium at Bragg primary frequency, whereas it increases at other frequencies. On the other hand, the resonance enhances when plate flexibility decreases and porosity increases. Further, Bragg resonance magnifies with a wide frequency band while shifting towards the left at higher incident angles. In this situation, structure deflection increases with the increased incident wave angle and diminishes for angles greater than a particular incident angle. Structure deflection increases with decreasing water-depth ratio in the presence of sloping plane bottom.

Dynamic Roughness Modeling of Seasonal Vegetation Effect: Case Study of the Nanakita River

Hydraulic models of rivers are essential for vulnerability assessment in disaster management. This study simulates the 2019 Typhoon Hagibis at the Nanakita River using a dynamic roughness model. The model estimates the roughness of the river on a pixel level from the relationship between the Manning roughness coefficient and the degree of submergence of vegetation. This degree is defined as the ratio of water depth to plant height. After validating the model, the effect of vegetation on the water level in different seasons from April 2020 to March 2021 was assessed. The vegetation area and height were obtained on a pixel level using unmanned aerial vehicle photogrammetry. The dynamic roughness model showed that the water level profile increased by 7.03% on average. The seasonal effect of vegetation was observed, revealing a strong correlation between variations in the vegetation conditions and water level profile. This approach may help mitigate flood damage by indicating the factors that can increase the risk of flooding.

Failure mechanism and vulnerability assessment of coastal box-girder bridge with laminated rubber bearings under extreme waves

Coastal box-girder bridges have wide applications in the near-shore transportation systems and many low-lying bridges are under serious threats from extreme waves. However, few researchers paid attention to the dynamic structural behaviors of coastal low-lying bridges under extreme wave conditions, which is crucial to the rational design of these bridges. In this study, a three-dimensional finite element model, including the local nonlinear bearing material model and wave loading importation from the computational fluid dynamics (CFD) simulations, is established to investigate the dynamic behavior of the bridge structure. Specifically, to provide a more scientific and precise evaluation for the dynamic behavior of coastal bridges, the laminated rubber bearing model is established at joints between the superstructure/box-girder and bent cap using solid elements. Three common failure modes, including the large lateral shear deformation of the rubber bearing, sliding between the girder and bearings, and overturning of the superstructure, are investigated in detail. To consider the uncertainty under different loading conditions, one surrogate model based on the support vector machine (SVM) is adopted to enhance the calculation efficiency of the vulnerability assessment for the coastal box-girder bridge. It is revealed that (a) The overturning and sliding failures are more likely to occur for the box-girder in submerged states, while the large lateral shear deformation for the bearing is prone to arise when the girder is elevated; (b) The wave height to water depth ratio has a significant influence on the safety of the bridge; and (c) The high failure probability indicates that appropriate countermeasures are necessary to improve the safety margin of the bridge.

Effect of submarine permafrost degradation on the vertical ground motions and vertical response spectrum of a single-degree-of-freedom system in polar ocean

Owing to global warming, the rise in sea temperature is causing degradation of submarine permafrost, which has an impact on the seismic responses of submarine strata. Based on the revised dynamics of nearly saturated frozen porous media, a simplified model of the vertical seismic responses of submarine permafrost is established considering the degradation of its upper layer, and an analytical solution is obtained using the Laplace transform method. The governing equation of a single-degree-of-freedom system on the seafloor is further proposed, and the vertical response spectrum is obtained using the numerical inverse transformation method. The numerical results show that the vertical ground motions of the seafloor agree well with those of saturated and nearly saturated soil layers with a free surface on land and under deep-water conditions. Parametric studies show that saturation strongly affects the vertical ground motions of the seafloor, and this effect is closely related to the water depth ratio. In addition, the structural stratum parameters, including the active layer thickness ratio, permafrost thickness, and temperature, have significant effects on the vertical ground motions of the seafloor and the vertical response spectrum of the submarine lumped parameter system. Therefore, attention should be paid to the impact of submarine permafrost degradation on the vertical seismic responses of oil and gas exploitation systems in polar oceans.

Nonlinear dynamic analysis of the deep-water bridge piers under combined earthquakes and wave actions

When the Stokes fifth-order wave is utilized to study the wave force of large-diameter bridge piers, the iterative method is usually utilized to solve the transcendental equations and then solve the wave parameter wavelength, coefficient and wave number. The solving process is particularly complicated, and the ratio of water depth and wavelength is generally assumed to be 0.1–0.15, which is suitable for shallow water depths and has not been investigated for deep water depths. In this study, the wave force and action point of the large-diameter rectangular section bridge pier under Stokes fifth-order wave action are derived, and the range of Stokes wave number is derived when the deep water level is constant. Combined with the functional analysis of transcendental equations, a program for calculating the Stokes fifth-order wave parameters is derived, and the approximate solution of the coefficient and wavelength of the Stokes wave is accurately and quickly solved. The dynamic nonlinear analysis of super deep-water large-diameter bridge pier under combined multi-dimensional earthquake and nonlinear wave action is investigated. It is found that nonlinear waves can significantly increase the dynamic response of deep-water bridge pier structure, but under combined wave and earthquake loadings on the deep-water bridge pier structure, and earthquakes play a dominant role. The influence of resonant waves and common linear waves on the dynamic response of large-diameter bridge piers in deep water depth is quite different. Resonant waves have a significant influence on the displacement response and stress response of deep-water bridge piers. When under two-dimensional earthquake and resonant wave independent loadings, the influence on the dynamic response of deep-water bridge pier structures is insignificant. When under combined earthquakes and waves loadings on the deep-water bridge pier structure, earthquakes play a significant role.

Evaluation of effective parameters of Manning roughness coefficients in HDPE culverts via kernel-based approaches

Abstract The prediction of Manning coefficients plays a prominent role in the estimation of head losses along culvert systems. Although the Manning coefficient is treated as a constant, previous studies showed the dependency of this coefficient on several parameters. This study aims to evaluate the effective parameters of the Manning roughness coefficient using intelligence approaches such as Gaussian process regression (GPR) and support vector machines (SVM), in which the input variables were considered as dimensionless and dimensional. In addition to the enhanced efficiency of the SVM approach compared to the GPR approach in model development with dimensionless input variables, the accuracy of model A(I) with input parameters of Fr (Froude) and y/D (the ratio of water depth to culvert diameter) and performance criteria of correlation coefficient (R) = 0.738, determination coefficient (DC) = 0.0962, root mean square errors (RMSE) = 0.0015 and R = 0.818, DC = 0.993 and RMSE = 0.0006 for GPR and SVM approaches were the highest. Thus, for the second category, a model with an input parameter of discharge (Q), hydraulic radius (RH), and culvert's slope (S0) showed good efficiency in predicting the Manning coefficient, in which the performance criteria of GPR and SVM approaches were (R = 0.719, DC = 0.949, RMSE = 0.0013) and (R = 0.742, DC = 0.991, RMSE = 0.007), respectively. Furthermore, developed OAT (one-at-a-time) sensitivity analysis revealed that relative depth y/D and Q are the most important parameters in the prediction of the Manning coefficient for models with dimensionless and dimensional input variables, respectively.

Air-sea interaction processes during hurricane Sandy: Coupled WRF-FVCOM model simulations

A fully-coupled atmospheric-ocean model was developed by coupling WRF (Weather Research and Forecasting Model) with FVCOM (the unstructured-grid, Finite-Volume Community Ocean Model) through the Earth System Model Framework (ESMF). The coupled WRF-FVCOM is configured with either hydrostatic or non-hydrostatic oceanic dynamics and can run with wave-current interactions. We applied this model to simulate the 2012 Hurricane Sandy in the western Atlantic Ocean. The experiments examined the impact of air-sea interactions on Sandy’s intensity/path and oceanic responses under hydrostatic and non-hydrostatic conditions. The results showed that the increased storm wind rapidly deepened the mixed layer depth when ocean processes were included. Intense vertical mixing brought cold water in the deep ocean towards the surface, producing a cold wake within the maximum wind zone underneath the storm. This process led to a sizeable latent heat loss from the ocean within the storm, and hence rapid air temperature and vapor mixing ratio drop above the sea surface. The storm intensified as the central sea-level pressure dropped. Improving air pressure simulation with ocean processes tended to reduce the storm size and strengthen its intensity, providing a better simulation of hurricane path and landfall. Turning on the non-hydrostatic process slightly improved the hurricane central sea-level pressure simulation and intensified the winds on the right side of the hurricane center. Hydrostatic and non-hydrostatic coupled WRF-FVCOMs captured Sandy-induced rapidly-varying flow over the shelf and the wind-induced surge level at the coast. The coupled models predicted a higher water elevation around the coastal areas where Sandy made landfall than the uncoupled model. The uncoupled and coupled models both showed more significant oceanic responses on the right side of the hurricane center, with a maximum during the Sandy crossing period when the clockwise-rotating frequency of Sandy wind was close to the local inertial frequency. The area with a maximum response varied with Sandy’s translation speed, more prominent in the deep region than over the slope, and more substantial under the non-hydrostatic condition. The simulated ocean responses agreed with the theoretical work of Price (1981). The nonhydrostatic experiments suggest that to resolve a fully storm-induced convection process, the oceanic model grid configuration should meet the O(1) criterion for the ratio of local water depth to the model horizontal resolution.

Live-bed pier scour in supercritical open-channel flows

Under a flow in supercritical regime, depending on the pier width to water depth ratio, the flow pattern around a bridge pier can take the form of a wall-jet-like bow wave or a detached hydraulic jump. The present work aims at analysing the maximum scour depth at piers in both flow patterns. A dedicated experimental set-up was used to produce the live-bed scour experiments, varying the inflow velocity and pier diameter. During the experiments, scour developed very rapidly, achieving equilibrium conditions after few minutes. No major differences between the maximum scour depth in the wall-jet-like bow wave and detached hydraulic jump cases were observed. Measured scour depths were of comparable magnitude and followed similar tendencies with controlling parameters as in subcritical flows. Scour formulas for piers in subcritical flow thus achieve a good accuracy in prediction of maximum scour depth at piers in supercritical flows.

Experimental study of the dam-break waves in triangular channels with a sloped wet bed

There has been little study on the impact of bottom slope on dam break wave propagating along a triangular wet channel. In this study, laboratory experiments are conducted in a large-scale triangular laboratory flume, covering a range of bed slope and rations of upstream over downstream water depth. Water surface and stage hydrograph wave height are collected using the non-intrusive measurement methods, which are used to obtain wave characteristics. Results show that for dry bed, the wavefront celerity increases with the increase of the slope; while for a wet bed, the wavefront celerity decreases as the slope increases and the decrease rate is significantly reduced. Moreover, the wavefront celerity decreases with the increase of water depth ratio. The maximum wave height at each measurement location decreases with the increase of water depth ratio. According to the arrival of the maximum wave height, the dam-break wave can be classified into two modes, namely Type A in which wave height gradually rises to the maximum when flow reaches and Type B in which the maximum wave height appears at the beginning of the dam failure. This study is useful for in-depth understanding of the dam-break wave evolution in sloping triangular wet rivers.

Hydrodynamic analysis of ship manoeuvrability in shallow water using high-fidelity URANS computations

The manoeuvring performance of a ship in shallow water is substantially different from its performance in deep water, attributed to shallow water effects caused by the presence of a finite water depth. Without a doubt a ship will navigate in areas of shallow water at various times during its operational life (such as when approaching harbours or ports), which underscores the importance of understanding the shallow water effects on ship manoeuvrability. In the present paper, the manoeuvrability of the KRISO Container Ship (KCS) model in different shallow water conditions was comprehensively analysed by means of the unsteady Reynolds-Averaged Navier-Stokes (URANS) computations coupled with the equations of rigid body motion with full six degrees of freedom (6DOF). A dynamic overset grid approach was implemented to allow the ship hull to move in 6DOF in a computational domain and to enable the rudder to be deflected according to a rudder controller for free-running manoeuvres. A series of manoeuvring simulations were performed in shallow waters with water depth to draft ratios varying between 1.2 and 4.0, and partially validated with the available experimental data from a free running test. The numerical results revealed that the ship advance, transfer, and tactical diameter mainly increased with the decrease in the ratio of water depth to draft, closely associated with the complicated interactions between the hull wake, boundary layer, propeller, vortex, and sea floor.

Investigation on a Large-Scale Braceless-TLP Floating Offshore Wind Turbine at Intermediate Water Depth

Tension leg platform (TLP) is a cost-effective and high-performance support structure for floating offshore wind turbine (FOWT) because of its small responses in heave, pitch, and roll with the constraint of the tendons. China, as the largest market of offshore wind energy, has shown a demand for developing reliable, viable floating platform support structures, especially aiming at the intermediate water depth. The present paper described a newly proposed 10-MW Braceless-TLP FOWT designed for a moderate water depth of 60 m. The numerical simulations of the FOWT are carried out using the coupled aero-hydro-servo-elastic-mooring calculation tool FAST. The measured wind and wave data of the target site close to the Fujian Province of China were used to evaluate the performance of the FOWT under the 100-, 50-, 5-, and 2-year-return stochastic weather conditions. The natural periods of the platform in surge, sway, heave, pitch, roll, and yaw were found to be within the range recommended by the design standard DNV-RP-0286 Coupled Analysis of Floating Wind Turbines. The largest surge of the water depth ratio among all the load cases was 15%, which was smaller than the admissible ratio of 23%. The tower top displacements remained between −1 m and 1 m, which were at a similar order to those of a 10-MW monopile-supported offshore wind turbine. The six tendons remained tensioned during the simulation, even under the operational and extreme (parked) environmental conditions. The Braceless-TLP FOWT showed an overall satisfying performance in terms of the structural stability and illustrates the feasibility of this type of FOWT at such a moderate water depth.

Integrated approach to assess resonance between basin eigenmodes and moored ship motions with wavelet transform analysis and proposal of operational thresholds

Waves with periods between 25 s and some minutes can amplify the motions of moored ships, which may result in terminal downtimes and compromise safety. The purpose of this work is twofold: (i) studying infragravity waves and their influence on moored ship motions, including the definition of operational thresholds and (ii) developing a novel and integrated approach to identify and assess resonance situations using wavelet transform analysis. The resonant modes of the harbor basin were identified using a numerical model validated with full-scale data. The motions of five similar LPG vessels moored at two adjacent jetties were analyzed, both in the frequency and frequency–time domains. It was concluded that surge is the most important motion at the berth that has greater operational problems. Moreover, the infragravity motion periods vary with the mooring line pretension and are proportional to the ratio of water depth to vessel draft. Three episodes of mooring line breaking were attributed to large infragravity surge oscillations. In addition, operational thresholds for basin-vessel resonance situations were defined based on the port tide gauge data. A significant wave height of 0.075 and 0.010 m for the 30–65 s period band was established for LPGs and oil tankers, respectively.

Effects of the gap on the local scour around two tandem piles in shallow flows

Local scour around two tandem piles in shallow water is numerically investigated under clear-water conditions. The characteristics of the scour process, depth, and flow fields are shown to be significantly influenced by the pile gap ratio (G/D = 1.0–5.0) and water depth ratio (h/D = 0.5–3.0). Under the same G/D, the dimension of the scour hole and the maximum scour depth around two piles become larger with the increase of h/D. Under the shallowest water depth condition (h/D = 0.5), the scour dimension and maximum scour depth of the rear pile are larger than that of the front pile, due to the weak upflow and strong downflow upstream of the rear pile. However, under the deepest water depth condition (h/D = 3.0), the scour hole becomes smaller than that of the front pile, due to the significant upflow downstream the front pile by less confinement from the high water surface. The vortex shedding patterns and their interaction with the sediment transport in different G/D and h/D cases are also discussed.

Comparison of shallow water effect on a monohull and chine catamaran

Many modifications to the hull shape have been made to obtain the optimum hull to reduce resistance. Various modifications of hull shape, as well as with the addition of the number of hulls, become multihulls. This study conducted a comparative study of monohull rounded and chine catamarans on the squat factor by varying the water depth ratio h/T 1.2, 1.3, and 1.5. The analysis is also carried out on the sinkage and trim factors by varying the ship’s trim with changes in LCG points and variations in speed. The simulation results on the effect of depth ratio show that chine catamaran has a squat effect lower than monohull at Fr 0.5. The depth ratio h/T 1.2 of 9.83%, h/T 1.3 of 18.3%, and the h/T 1.5 of 20.69%. At a lower speed Fr<0.3, the monohull has a lower squat effect than chine catamaran. For the effect of 10% LCG trim by stern on the sinkage factor, chine catamaran has a lower value than monohull at Fr 0.5. The analysis results show that chine catamaran has a sinkage effect of up to 40.4% lower than monohull at a ratio of h/T 1.3. In trim by bow conditions, chine catamaran had a lower sinkage effect than monohull at Fr 0.5 with the most significant deviation of 34.21% at a ratio of h/T 1.5. The overall analysis shows that monohull has a remarkable effect on shallow water at Fr<0.3. While at higher speeds, catamarans have a lower influence on the squat, sinkage and trim factors in shallow water conditions.