scholarly journals THE USE OF ARRAY PROCESSORS FOR NUMERICAL MODELLING OF TIDAL ESTUARY DYNAMICS

1980 ◽  
Vol 1 (17) ◽  
pp. 142
Author(s):  
D. Prandle ◽  
E.R. Funke ◽  
N.L. Crookshank ◽  
R. Renner
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Hybrid Model ◽  
Numerical Models ◽  
Computer Time ◽  
Scale Model ◽  
Hybrid Modelling ◽  
Tidal Propagation ◽  
Physical Scale ◽  
Array Processors

The use of array processors for the numerical modelling of estuarine systems is discussed here in the context of "hybrid modelling", however, it is shown that array processors may be used to advantage in independent numerical simulations. Hybrid modelling of tidal estuaries was first introduced by fiolz (1977) and later by Funke and Crookshank (1978). In a hybrid model, tidal propagation in an estuary is simulated by dynamically linking an hydraulic (or physical) scale model of part of the estuary to a numerical model of the remaining part in a manner such that a free interchange of flow occurs at the interface(s). Typically, the elevation of the water surface at the boundary of the scale model is measured and transmitted to the numerical model. In return, the flow computed at the boundary of the numerical model is fed directly into the scale model. This approach enables the extent of the scale model to be limited to the area of immediate interest (or to that area where flow conditions are such that they can be most accurately simulated by a scale model). In addition, since the region simulated by the numerical model can be extended almost indefinitely, the problems of spurious reflections from downstream boundaries can be eliminated. In normal use, numerical models are evaluated on the basis of computing requirements, cost and accuracy. The computer time required to simulate one tide cycle is, in itself, seldom of interest except in so far as it affects the above criteria. However in hybrid modelling this parameter is often paramount since concurrent operation of the numerical and scale models requires that the former must keep pace with the latter. The earlier hybrid model of the St. Lawrence (Funke and Crookshank, 1978) involved a one-dimensional numerical model of the upstream regions of the river. However, future applications are likely to involve extensive two-dimensional numerical simulation.

scholarly journals FLOW COMPUTATIONS NEARBY A STORM SURGE BARRIER UNDER CONSTRUCTION WITH TWO-DIMENSIONAL NUMERICAL MODELS

1986 ◽  
Vol 1 (20) ◽  
pp. 143
Author(s):  
H.E. Klatter ◽  
J.M.C. Dijkzeul ◽  
G. Hartsuiker ◽  
L. Bijlsma
Keyword(s):  
Numerical Model ◽  
Storm Surge ◽  
Field Data ◽  
Numerical Models ◽  
Flow Patterns ◽  
Scale Model ◽  
Energy Losses ◽  
Local Energy ◽  
Two Dimensional ◽  
Physical Scale

This paper discusses the application of two-dimensional tidal models to the hydraulic research for the storm surge barrier in the Eastern Scheldt in the Netherlands. At the site of the barrier local energy losses dominate the flow. Three methods are discussed for dealing with these energy losses in a numerical model based on the long wave equations. The construction of the storm surge barrier provided extensive field data for various phases of the construction of the barrier and these field data are used as a test case for the computation at methods developed. One method is preferred since it gives good agreement between computations and field data. The two-dimensional flow patterns, the discharge and the head-difference agree well,, The results of scale model tests were also available for comparison. This comparison demonstrated that depth-averaged velocities, computed by a two-dimensional numerical model, are as accurate as values obtained from a large physical scale model. Even compicated flow patterns with local energy losses and sharp velocity gradients compared well.

Physical and numerical modelling of sediment guiding walls in an alpine river

2021 ◽  
Author(s):  
Jakob Siedersleben ◽  
Marco Schuster ◽  
Dennis Ties ◽  
Benjamin Zwick ◽  
Markus Aufleger ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Power Plants ◽  
Sediment Management ◽  
Design Flow ◽  
Scale Model ◽  
Surface Measurement ◽  
Management Options ◽  
Erosion And Deposition ◽  
Alpine River

<p>The presented work is part of the optimization of the sediment management at the hydroelectric powerplants in Reutte/Höfen in Austria. The weirs of the two powerplants are situated at the alpine river Lech, located about 3 km upstream of the Lechaschau gauge (A=1012.2 km²). Totally five sluice gates and a fixed overflow weir are controlling the upstream reservoir, being subjected to high rates of coarse bed load material. In frame of a coupled approach of physical and numerical modelling, different options to (i) avoid/minimize sediment deposition and (ii) allow improved sediment flushing were tested and optimized. Besides a lowering of energy losses (reduced spilling times) the reduction of depositions downstream close to the turbine outlet were considered.</p><p>The physical model covers the hydropower and weir system of both power plants within a stretch of 400m / 150m using a model scale of 1:25. Investigated situations covered periods of reservoir sedimentation, flushing of the reservoir and typical flood flow situations (e.g. HQ1 and an unsteady HQ5 event). For model parametrization, sediment samples to quantify size distribution were taken in the field. Sediment inputs to the model were realized dynamically and were required (due to scaling effects) to exclude cohesive fractions having a minimum particle size of 0.5 mm. The full-area surface measurement of the river bed was made by means of airborne laser bathymetry and echo sounding.</p><p>As part of an optimization of the overall sediment management strategy, the focus of the presented research is on the western located runoff power plant Höfen. Via a lateral water intake, a maximum design flow of 15 m³/s is withdrawn causing that the intake structure is subjected to sediment depositions. Within the described scale model (1:25) and a partial scale model (1:15) covering the western side, several management options and configurations of sediment guiding walls were tested. Erosion and deposition as well as the transported material are assessed by 3D laser scanning and permanent monitoring of transported sediment load entering and leaving the scale model.</p><p>Complementary, a 2D hydro numerical model using a layer based multi fraction approach for sediment transport is set up for an extended area to simulate the morpho-dynamic behavior. The numerical model covers the whole weir system and 750 m of the upstream part of the Lech. The simulations made were realized at nature scale and allowed to mimic the erosion and deposition pattern obtained within the physical modelling for different tested options. Regardless of a chosen guiding wall setup, the results showed that each one is compromise between sediment defense and the effectiveness of the subsequent flushing processes.</p>

3D numerical modeling of sediment handling techniques in a hydro power reservoir

2020 ◽  
Author(s):  
Diwash Lal Maskey ◽  
Dipesh Nepal ◽  
Daniel Herman ◽  
Gabriele Gaiti ◽  
Nils Rüther
Keyword(s):  
Numerical Model ◽  
Guide Vane ◽  
Scale Model ◽  
Bed Load ◽  
3D Numerical Modeling ◽  
Deposition Pattern ◽  
Flow Measurements ◽  
Reservoir Volume ◽  
Physical Scale ◽  
3D Numerical Model

<p>Sedimentation of small as well as large water storage reservoir has become a major issue. Due to the fact that we observe a 1% decrease of reservoir volume every year due to sedimentation and that the largest part of the reservoirs have been built between 70 and 40 years ago, many HPPs are confronted with the threatening scenario that soon the active storage and therefore their lifetime is dramatically diminished. Due to the above mentioned combination, active and sustainable sediment management has become the last option to retain or preferable enlarge the left-over reservoir volume. There are several options for a sustainable sediment handling, each for a different boundary condition, which must be evaluated carefully in order to be successful. For a successful choice, design and conduction of a sediment handling technique, usually a physical scale model will be conducted. Physical scale model have the advantage that there is a lot of experience in conducting these models and that they are illustrative. The disadvantage of scale models is that there are restrictions in the use of certain sizes of sediments due to scaling issues and that they are rather expensive.</p><p>This study attempt to use a 3D numerical model to overcome the above mentioned disadvantages and to serve as an additional source of alternatives in finding the right sediment handling techniques in reservoirs with high discharges of suspended and bed load. The goal is to simulate several flood events in order to gain insights in the current situation as well as to have a better understanding of the physical processes in the reservoir. This will support and positive influence the sustainable design of sediment handling techniques. The numerical model will be verified with flow measurements a physical model study and with bathymetry measurements from field observations. Based on the actual deposition pattern and the given input data, different sediment handling techniques are planned and conducted by means of the numerical model. The results show that the 3D numerical model is able to simulate sediment transport deposition pattern, bed load guide vane structures, as well as bed load diversion structures.</p>

scholarly journals Numerical Modeling of Flow Field in Morning Glory Spillways and Determining Rating Curve at Different Flow Rates

2016 ◽  
Vol 2 (9) ◽  
pp. 448-457 ◽  
Author(s):  
Mohammad Reza Enjilzadeh ◽  
Ebrahim Nohani
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Numerical Modelling ◽  
Relative Error ◽  
Numerical Models ◽  
Discharge Rate ◽  
Morning Glory ◽  
Physical Models ◽  
Rating Curve ◽  
Inlet Conditions

Morning glory spillways with drop inlets are normally employed in dams built on narrow valleys or placed on steep slopes. In Iran, morning glory spillways have been commonly used in large Dam projects such as Sefidrood dam, Alborz dam, and Haraz dam. Physical models should be built to accurately determine hydraulic parameters of the flow and flow field in spillways. Establishment of a physical model involves extravagant costs and conditions that cannot be justified in some cases. Therefore, suitable numerical models can be proposed for such circumstances. Using FLOW3D numerical models, 3-dimensional numerical modelling of the flow was calibrated and validated by experimental information associated with morning glory spillway of Alborz dam and accuracy of numerical modelling was determined by relative error of numerical model. So it was attempted to determine flow pattern and control conditions of morning glory spillways in different modes using boundary conditions, inlet conditions and grid spacing of flow field and project rating curve of morning glory spillways. According to the results of numerical model, relative error of numerical modelling equals 6.4% for calculating discharge rate of the spillways. Numerical modelling error is 7.6% for determining depth parameter of the flow in spillway crest in comparison with experimental results.

A Hybrid (Numerical-physical) Model of the Left Ventricle

2001 ◽  
Vol 24 (7) ◽  
pp. 456-462 ◽  
Author(s):  
G. Ferrari ◽  
M. Kozarski ◽  
C. De Lazzari ◽  
F. Clemente ◽  
M. Merolli ◽  
...  
Keyword(s):  
Numerical Model ◽  
Hybrid Model ◽  
Time Course ◽  
Numerical Models ◽  
Open Loop ◽  
Physical Models ◽  
Gear Pump ◽  
Arterial Tree ◽  
Pump System ◽  
Output Flow

Hydraulic models of the circulation are used to test mechanical devices and for training and research purposes; when compared to numerical models, however, they are not flexible enough and rather expensive. The solution proposed here is to merge the characteristics and the flexibility of numerical models with the functions of physical models. The result is a hybrid model with numerical and physical sections connected by an electro-hydraulic interface - which is to some extent the main problem since the numerical model can be easily changed or modified. The concept of hybrid model is applied to the representation of ventricular function by a variable elastance numerical model. This prototype is an open loop circuit and the physical section is built out of a reservoir (atrium) and a modified windkessel (arterial tree). The corresponding equations are solved numerically using the variables (atrial and arterial pressures) coming from the physical circuit. Ventricular output flow is the computed variable and is sent to a servo amplifier connected to a DC motor-gear pump system. The gear pump, behaving roughly as a flow source, is the interface to the physical circuit. Results obtained under different hemodynamic conditions demonstrate the behaviour of the ventricular model on the pressure-volume plane and the time course of output flow and arterial pressure.

Modeling and Experiments on an Oscillating Water Column Using a Self-Adaptive Air Turbine and Shutter

2013 ◽  
Author(s):  
Patrick Lorenz ◽  
Richard W. Kimball ◽  
Frank DiBella ◽  
Richard Smith ◽  
Scott Ring
Keyword(s):  
Numerical Model ◽  
Water Column ◽  
Potential Flow ◽  
Numerical Models ◽  
Air Flow ◽  
Chamber Pressure ◽  
Oscillating Water Column ◽  
Cavity Pressure ◽  
Wells Turbine ◽  
Physical Scale

This paper presents model-scale measurements and numerical models of a floating oscillating water column (OWC) system, consisting of an air cavity coupled with a Wells-type turbine energy extraction device. As waves travel through the OWC, air pressure cycles are generated. The oscillating water column captures the resulting pneumatic energy by directing the chamber pressure and air flow through the Wells turbine. A special feature of the system is a shuttering device that momentarily interrupts turbine air flow. The shuttering device is used to control the cavity pressure for optimum turbine performance. Shuttering in this manner can be shown to improve overall system efficiency up to 20% pressure. Physical scale models of the OWC system were tested in a wave tank at Maine Maritime Academy (MMA) at 1/30th scale as well as elastomeric diaphragm testing at 1/15th scale, under various conditions. Data from these tests, including cavity pressure response, turbine flow rate, and computed fluid power are discussed. In addition, numerical models of the system were developed using a parametric spring-mass-dashpot methodology and as well as a potential flow model derived for cavity geometry in a global wave field (see section 3). This paper describes the OWC system with adaptive shutter; comparison of experimental measurements to numerical model predictions; numerical model implementation and measurements of energy absorption/resonant effects within the chamber; and a potential flow derivation.

Cold Cap Grout Formulation for Waste Containment at DOE Site, Hanford, Washington

1991 ◽  
Vol 245 ◽  
Author(s):  
Lillian D. Wakeley ◽  
James J. Ernzen
Keyword(s):  
Numerical Models ◽  
Bentonite Clay ◽  
Department Of Energy ◽  
Scale Model ◽  
Natural Sand ◽  
Near Surface ◽  
Volume Stability ◽  
Performance Requirements ◽  
Physical Scale ◽  
Class F Fly Ash

ABSTRACTWES developed a grout to be used as a cold (non-radioactive) cap or void-fill material between the solidified low-level waste and the cover blocks of near-surface disposal vaults at the U.S. Department of Energy (DOE) Hanford Facility. The project consisted of formulation and evaluation of candidate grout, followed by a physical scale-model test to verify grout performance under project-specific conditions and provide data to verify numerical models of stresses and isotherms inside the Hanford demonstration vault. Evaluation of unhardened grout included segregation, bleed, flow, and working time. For hardened grout, strength, volume stability, thermal heat rise, and geochemical compatibility with surrogate wasteform grout were examined.The grout was formulated to accommodate unique environmental boundary conditions (vault temperature = 45 °C) and exacting regulatory requirements (mandating less than 0.1% shrinkage with no expansion and no bleeding); and to remain pumpable for a minimum 2 hr. A grout consisting of API Class H cement, an ASTM C 618 Class F fly ash, sodium bentonite clay, and a natural sand from the Hanford area met all performance requirements in laboratory studies.

Research on Underwater Static Electric Field for Warship Based on Hybrid Model

2015 ◽  
Vol 713-715 ◽  
pp. 925-929 ◽  
Author(s):  
Qiang Bian ◽  
De Hong Liu ◽  
Xiang Jun Wang
Keyword(s):  
Electric Field ◽  
Hybrid Model ◽  
New Method ◽  
Scale Model ◽  
Static Electric Field ◽  
Current Line ◽  
Horizontal Current ◽  
Physical Scale

A new method that is to model the electric field of a warship with a hybrid model which is “horizontal current line plus discrete dipoles” is put forward. The majority of the electric field is simulated by horizontal current line, and several discrete dipoles can be used to modify the detail of the electric field. This method is expected to have same precision but more stabilization and less calculation. The method is validated by experiments using a physical scale model of ship.

Solidification of Phase Change Material Nanocomposite Inside a Finned Heat Sink: A Macro Scale Model of Nanoparticles Distribution

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Santosh Kumar Sahoo ◽  
Prasenjit Rath ◽  
Mihir Kumar Das
Keyword(s):  
Numerical Model ◽  
Phase Change ◽  
Phase Change Material ◽  
Finite Volume ◽  
Heat Sink ◽  
Numerical Models ◽  
Scale Model ◽  
Transfer Model ◽  
Macro Scale ◽  
Change Material

The present work aims at developing a heat transfer model for phase change material nanocomposite (PCMNC)-based finned heat sink to study its heat rejection potential. The proposed model is developed in line with the binary alloy formulation for smaller size nanoparticles. The present study gives a more insight into the nanoparticle distribution while the nanocomposite is undergoing phase change. The nanocomposite is placed in the gap between the fins in a finned heat sink where solidification occurs from the top and lateral sides of fins. The proposed numerical model is based on finite volume method. Fully implicit scheme is used to discretize the transient terms in the governing transport equations. Natural convection in the molten nanocomposite is simulated using the semi-implicit-pressure-linked–equations-revised (SIMPLER) algorithm. Nanoparticle transport is coupled with the energy equation via Brownian and thermophoretic diffusion. Enthalpy porosity approach is used to model the phase change of PCMNC. Scheil rule is used to compute the nanoparticle concentration in the mixture consisting of solid and liquid PCMNC. All the finite volume discrete algebraic equations are solved using the line-by-line tridiagonal-matrix-algorithm with multiple sweeping from all possible directions. The proposed numerical model is validated with the existing analytical and numerical models. A comparison in thermal performance is made between the heat sink with homogeneous nanocomposite and with nonhomogeneous nanocomposite. Finally, the effect of spherical nanoparticles and platelet nanoparticles to the solidification behavior is compared.

scholarly journals BLOCK REVETMENT DESIGN WITH PHYS. AND NUM. MODELS

1988 ◽  
Vol 1 (21) ◽  
pp. 160 ◽  
Author(s):  
A. Bezuijen ◽  
J. Wouters ◽  
C. Laustrup
Keyword(s):  
Numerical Models ◽  
Scale Model ◽  
Pressure Loading ◽  
Wave Pressure ◽  
Flow Equations ◽  
Physical Scale ◽  
The Stability ◽  
Filter Layer ◽  
Sea Coast ◽  
North Sea Coast

A combination of a physical model and numerical models has been used in the design of a block revetment for the Danish North Sea coast. The wave pressure loading on the revetment during design conditions was investigated in a physical scale model. The measured wave pressures were used as a boundary condition for the numerical models. Solutions for the flow equations through the coverlayer, filter layer and subsoil were then obtained in the numerical models, taking into account the influence of turbulence. With these solutions the stability of the coverlayer and subsoil was evaluated. The paper presents a description of the various models and information about the design of the revetment.

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