scholarly journals THE EFFECT OF EMBANKMENT CREST WIDTH ON COMBINED OVERFLOW AND WAVE OVERTOPPING

2012 ◽  
Vol 1 (33) ◽  
pp. 28
Author(s):  
David Jones ◽  
Dominic Reeve ◽  
Qingping Zou
Keyword(s):  
Wave Model ◽  
Experimental Results ◽  
Navier Stokes ◽  
Wave Overtopping ◽  
Current Design ◽  
Reynolds Averaged Navier Stokes ◽  
The Difference

In this paper a Reynolds-averaged Navier-Stokes based wave model (RANS) has been used to investigate how the discharge caused by combined overflow and wave overtopping of embankments is influenced by embankment crest width. The results demonstrate that embankments with a narrower crest width can expect significantly increased discharge in accordance with that expected for flow over weirs. The experimental results have been used to explain the difference in discharge found with the current design formulae for combined overflow and wave overtopping.

scholarly journals Perhitungan Nilai Maksimum Thrust, Torque, dan Efficiency Propeller Tipe B-4 Series pada Kapal Tugboat dengan Modifikasi Diameter, Rake, dan Pitch menggunakan Metode Komputasi

2021 ◽  
Vol 5 (1) ◽  
pp. 63-78
Author(s):  
Kelly Cristin Prananda Lumbanraja ◽  
Deddy Chrismianto ◽  
Samuel Samuel
Keyword(s):  
Turbulent Flow ◽  
Computational Methods ◽  
Cfd Simulation ◽  
Experimental Results ◽  
Navier Stokes ◽  
Ship Propulsion ◽  
Reynolds Averaged Navier Stokes ◽  
Push And Pull ◽  
Maximum Thrust ◽  
Minimum Torque

ABSTRAKKapal tugboat digunakan untuk membantu kapal yang akan masuk atau keluar pelabuhan. Untuk mendorong dan menarik kapal maka diperlukan propeller sebagai mesin penggerak kapal. Kinerja propeller pada kapal tugboat sangat vital dalam menunjang fungsi tugboat tersebut. Pada penelitian ini akan melakukan modifikasi pada rake, diameter, dan pitch propeller B-Series pada kapal tugboat dengan metode komputasi sehingga diperoleh nilai efficiency yang paling baik. Simulasi pada penelitian ini akan menggunakan persamaan Reynolds-Averaged Navier Stokes (RANS) dan mendiskripsikan aliran turbulen dengan menggunakan model k-ε dan k-ω. Hasil nilai torque, thrust, dan efficiency yang sudah disimulasikan akan di verifikasi dengan diagram Wageningen. Wageningen adalah karakteristik propeller B-series yang sudah dipublikasikan dari hasil eksperimen. Dari hasil simulasi CFD diperoleh kesimpulan torque paling minimum terletak pada modifikasi dengan rake 0°, pitch 1,36, dan diameter 1,3 pada rpm 180 sebesar 545,68 Nm. Modifikasi model propeller pada 230 rpm menggunakan diameter 1,4 m, rake 5° dan pitch 1,56 merupakan modifikasi yang direkomendasikan untuk memperoleh nilai thrust maksimum sebesar 12076 N, torque 3252,5 Nm dan mendapatkan nilai efisiensi yang paling optimum sebesar 0,7443.Kata kunci: Kapal Tugboat, Propeller, Diameter, Pitch, Rake ABSTRACTTugboat is used to pull or push ships which will enter or leave the harbor. To push and pull the ship, a propeller is needed as the ship propulsion. The performance of the propeller on the tugboat is vital for supporting the function of the tugboat. This research will make modifications to the rake, diameter, and pitch of the B-Series propeller on a tugboat using computational methods in order to achieve the best efficiency values. This simulation on this research will make use of Reynold-Averaged Navier Stokes (RANS) equation and describe the turbulent flow using the k-ε and k-ω. The results of the value torque, thrust, and efficiency that have been simulated will be verified with Wageningan diagram. Wageningen is the characteristics of the B-series propeller that have been published from the experimental results. From the CFD simulation result, it is concluded that the minimum torque is showed in the modification with a rake of 0°, a pitch of 1.36 and a diameter of 1.3 m at 180 rpm which is 545,68 Nm. Modification of the propeller model 230 rpm using a diameter of 1.4 m, 5° rake and a pitch of 1.56 is the recommended modification to obtain a maximum thrust value of 12076 N, torque of 3252.5 Nm and getting the most optimum efficiency value of 0.7443.Keywords: Tugboat, Propeller, Diameter, Pitch, Rake

scholarly journals MODELLING STORM SURGE WAVE OVERTOPPING OF SEAWALLS WITH NEGATIVE FREEBOARD

2011 ◽  
Vol 1 (32) ◽  
pp. 52
Author(s):  
David K Jones ◽  
Qingping Zou ◽  
Dominic E Reeve
Keyword(s):  
Boundary Condition ◽  
Storm Surge ◽  
Laboratory Data ◽  
Time History ◽  
Wave Model ◽  
Navier Stokes ◽  
Direct Wave ◽  
Wave Overtopping ◽  
Experimental Laboratory ◽  
Recorded Data

A Reynolds-averaged Navier-Stokes based wave model (RANS) is used to simulate storm surge wave overtopping of embankments. The model uses a wave generating boundary condition that accepts a wave time history as an input and reproduces the time history in the model. This allows a direct wave by wave simulation of recorded data. To investigate the success of the model at reproducing the wave generation, transformation and overtopping processes the model is compared with experimental laboratory data. A wave-by-wave comparison is performed for overtopping parameters such as discharge, depth and velocity. Finally the overtopping discharge predicted by the model is compared against design formulae.

Comparative Assessment of Turbulence Models for Unsteady Turbulent Flow Predictions in Single Rod Channel Configuration

2007 ◽  
Author(s):  
Kaushik Das ◽  
Debashis Basu ◽  
Scott Painter ◽  
Lane Howard ◽  
Steve Green
Keyword(s):  
Axial Flow ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Experimental Results ◽  
Navier Stokes ◽  
Mean Velocity ◽  
Reynolds Averaged Navier Stokes ◽  
Turbulent Models ◽  
Rsm Model ◽  
Channel Configuration

This paper compares different turbulent models for unsteady flow predictions for axial flow in a single rod channel configuration. The numerical analyses are carried out using the Reynolds Averaged Navier Stokes (RANS) equations and three different turbulent models. The predictions are compared with available experimental results. The three models considered in the present work include the RNG (Renormalization group) k-ε model, the realizable k-ε model, and the Reynolds stress model (RSM). With each model, an unsteady approach commonly referred to as URANS (Unsteady Reynolds Averaged Navier Stokes) solution is used. Predicted results are compared with available experimental results. The predicted time-averaged mean velocity and turbulent stresses are in good agreement with the available experimental results. Flow unsteadiness, which is important for determining heat, momentum, and mass transfer in the gap region, is presented through time histories and spectra of flow and turbulent quantities and their influence on the transportation of fluid across the gap is also explored. The effect of inflow unsteadiness on the solution is explored through comparing the flow field for a constant velocity inlet boundary condition as well as time-varying boundary conditions for the RSM model.

Experimental Investigation into Driver Behavior along Curved and Parallel Diverging Terminals of Exit Interchange Ramps

2021 ◽  
pp. 036119812199742
Author(s):  
Alberto Portera ◽  
Marco Bassani
Keyword(s):  
Design Stage ◽  
Lane Change ◽  
Age And Gender ◽  
Traffic Conditions ◽  
Current Design ◽  
The Difference ◽  
Safety Countermeasures ◽  
And Gender ◽  
Set Up ◽  
Curve Radius

Current design manuals provide guidance on how to design exit ramps to facilitate driving operations and minimize the incidence of crashes. They also suggest that interchanges should be built along straight roadway sections. These criteria may prove ineffective in situations where there is no alternative to terminals being located along curved motorway segments. The paper investigates driving behavior along parallel deceleration curved terminals, with attention paid to the difference in impact between terminals having a curvature which is the same sign as the motorway segment (i.e., continue design), and those having an opposite curvature (i.e., reverse design). A driving simulation study was set up to collect longitudinal and transversal driver behavioral data in response to experimental factor variations. Forty-eight drivers were stratified on the basis of age and gender, and asked to drive along three randomly assigned circuits with off-ramps obtained by combining experimental factors such as motorway mainline curve radius (2 values), terminal length (3), curve direction (2), and traffic conditions (2). The motorway radius was found to be significant for drivers’ preferred speed when approaching the terminal. Terminal length and traffic volume do not have a significant impact on either longitudinal or transversal driver outputs. However, the effect of curve direction was found to be significant, notably for reverse terminals which do not compel drivers to select appropriate speeds and lane change positions. This terminal type can give rise to critical driving situations that should be considered at the design stage to facilitate the adoption of appropriate safety countermeasures.

scholarly journals Revisiting Surface-Subsurface Exchange at Intertidal Zone with a Coupled 2D Hydrodynamic and 3D Variably-Saturated Groundwater Model

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 902
Author(s):  
Zhi Li ◽  
Ben R. Hodges
Keyword(s):  
Intertidal Zone ◽  
Coastal Wetlands ◽  
High Performance ◽  
Stokes Equations ◽  
Wave Model ◽  
Surface Flow ◽  
Richards Equation ◽  
Navier Stokes ◽  
Dynamic Surface ◽  
Flow Equations

A new high-performance numerical model (Frehg) is developed to simulate water flow in shallow coastal wetlands. Frehg solves the 2D depth-integrated, hydrostatic, Navier–Stokes equations (i.e., shallow-water equations) in the surface domain and the 3D variably-saturated Richards equation in the subsurface domain. The two domains are asynchronously coupled to model surface-subsurface exchange. The Frehg model is applied to evaluate model sensitivity to a variety of simplifications that are commonly adopted for shallow wetland models, especially the use of the diffusive wave approximation in place of the traditional Saint-Venant equations for surface flow. The results suggest that a dynamic model for momentum is preferred over diffusive wave model for shallow coastal wetlands and marshes because the latter fails to capture flow unsteadiness. Under the combined effects of evaporation and wetting/drying, using diffusive wave model leads to discrepancies in modeled surface-subsurface exchange flux in the intertidal zone where strong exchange processes occur. It indicates shallow wetland models should be built with (i) dynamic surface flow equations that capture the timing of inundation, (ii) complex topographic features that render accurate spatial extent of inundation, and (iii) variably-saturated subsurface flow solver that is capable of modeling moisture change in the subsurface due to evaporation and infiltration.

Reynolds-averaged Navier–Stokes simulation of hydrofoil effects on hydrodynamic coefficients of a catamaran in forced oscillation

2016 ◽  
Vol 231 (2) ◽  
pp. 364-383
Author(s):  
Amin Najafi ◽  
Mohammad Saeed Seif
Keyword(s):  
High Speed ◽  
Experimental Approach ◽  
Navier Stokes ◽  
Hydrodynamic Coefficients ◽  
Laboratory Equipment ◽  
Factors Affecting ◽  
High Frequencies ◽  
Frequency Independent ◽  
Reynolds Averaged Navier Stokes

Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using Reynolds-averaged Navier–Stokes method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly and requires meticulous laboratory equipment; therefore, utilizing the numerical methods and developing a virtual laboratory seem highly efficient. In this study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency-independent especially at high frequencies.

scholarly journals Identification of severe wind conditions using a Reynolds Averaged Navier-Stokes solver

2007 ◽  
Vol 75 ◽  
pp. 012053 ◽  
Author(s):  
N N Sørensen ◽  
A Bechmann ◽  
J Johansen ◽  
L Myllerup ◽  
P Botha ◽  
...  
Keyword(s):  
Navier Stokes ◽  
Reynolds Averaged Navier Stokes
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