scholarly journals A SCHEMATIZATION OF ONSHORE-OFFSHORE TRANSPORT

1974 ◽  
Vol 1 (14) ◽  
pp. 51 ◽  
Author(s):  
D.H. Swart
Keyword(s):  
Sediment Transport ◽  
Sandy Beaches ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Coastal Processes ◽  
Schematic Model ◽  
Empirical Relationships ◽  
Physically Based ◽  
Offshore Transport

The investigation reported herein covers two aspects of the schematization of coastal processes on sandy beaches in a direction perpendicular to the coastline, viz.: (1) the prediction of equilibrium beach profiles and (2) the corresponding offshore sediment transport due to wave action. A physically-based schematic model of the onshore-offshore profile development was tested on available small-scale and full-scale model tests and physically-based empirical relationships were derived to enable the application of the model to both small-scale and prototype conditions.

scholarly journals UNDISTORTED FROUDE MODEL FOR SURF ZONE SEDIMENT TRANSPORT

1986 ◽  
Vol 1 (20) ◽  
pp. 95 ◽  
Author(s):  
D.L. Kriebel ◽  
W.R. Dally ◽  
R.G. Dean
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Surf Zone ◽  
Scale Effects ◽  
Scale Model ◽  
Small Scale ◽  
Wave System ◽  
Governing Parameter ◽  
Fall Time ◽  
Offshore Transport

Small scale movable bed wave tank experiments were carried out according to undistorted Froude model laws with the sediment fall time, H/wT, as the governing parameter for scaling the model sediment. Four questions addressed in this study included: (a) the ability to reproduce larger scale model results for both erosional and accretive conditions, (b) the effects of more realistic concave upward initial beach profiles instead of the more usual planar initial slopes, (c) the criterion for onshore-offshore sediment transport, and (d) the capability of the model to simulate post-storm recovery. Based on a comparison with large scale results of Saville (1957), it was found that the model provided good agreement for erosive conditions. For accretive conditions, the results were less conclusive although the general patterns of profile change were similar. The final beach profiles resulting from concave upward initial profiles were found to be substantially different from those for an initially planar profile. It appears that the initially planar profile unrealistically affects the breaker type and results in a more pronounced longshore bar and offshore slopes that are steeper than found in nature. Tests conducted to evaluate the criterion separating onshore-offshore transport suggested a higher value of the fall time parameter, H/wT, than was originally proposed by Dean (1973); this is interpreted to be due to scale effects in most of the model data used in the original development. Tests to simulate post-storm recovery were affected by the presence of "reflection bars" associated with a partial standing wave system. The reflection bars appear to strongly affect the sediment transport limiting the post-storm profile recovery. The most effective recovery was induced by continually changing wave conditions to maintain the wave breakpoint slightly landward of the bar crest.

Drilling Riser VIV Tests With Prototype Reynolds Numbers

2013 ◽  
Author(s):  
Halvor Lie ◽  
Henning Braaten ◽  
Jamison Szwalek ◽  
Massimiliano Russo ◽  
Rolf Baarholm
Keyword(s):  
Cross Flow ◽  
Effect Study ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Scaling Effects ◽  
Research Activity ◽  
Forced Motion ◽  
Auxiliary Lines ◽  
Viv Suppression

For deep-water riser systems, Vortex Induced Vibrations (VIV) may cause significant fatigue damage. It appears that the knowledge gap of this phenomenon is considerable and this has caused a high level of research activity over the last decades. Small scale model tests are often used to investigate VIV behaviour. However, one substantial uncertainty in applying such results is scaling effects, i.e. differences in VIV response in full scale flow and small scale flow. To (partly) overcome this obstacle, a new innovative VIV test rig was designed and built at MARINTEK to test a rigid full scale riser model. The rigid riser model is mounted vertically and can either be elastically mounted or be given a forced motion. In the present version, the cylinder can only move in the cross-flow (CF) direction and is restricted in the in-line (IL) direction. The paper reports results from a drilling riser VIV experiment where the new rest rig has been used. The overall objective of the work is to study possible VIV suppression to improve operability of retrievable riser systems with auxiliary lines by adding riser fins. These fins are normally used as devices for protection of the auxiliary lines. The test program has recently been completed and analysis is an on-going activity. However, some results can be reported at this stage and more results are planned to be published. A bare riser model was used in a Reynolds number (Rn) scaling effect study. The riser model was elastically mounted and towed over a reduced velocity range around 4 – 10 in two different Rn ranges, 75 000 – 192 000 (subcritical regime) and 347 000 – 553 000 (critical regime). The difference in the displacement amplitude to diameter ratio, A/D, is found to be significant. The elastically mounted riser was also towed with various drilling riser configurations in order to study VIV/galloping responses. One configuration included a slick joint riser model with 6 kill & choke lines; another has added riser fins too. The riser model is based on a specific drilling riser and the kill and choke lines have various diameters and have a non-symmetrical layout. The various riser configurations have also been used in forced motion tests where the towed model has been given a sinusoidal CF motion. Forces have been measured. Determination of the force coefficients is still in progress and is planned to be reported later. Scaling effects appear to be a significant uncertainty and further research on the subject is recommended. The slick joint drilling riser configuration generally increased the displacements compared to displacements of the bare riser model. The drilling riser configuration with protection fins, kill and choke lines generally reduced the displacements compared to displacements of the bare riser model. For both riser systems, tests showed that the response is sensitive to the heading of the current.

Small and Full-Scale Modeling for the Application of Wall Solar Chimneys

2016 ◽  
Author(s):  
David Park ◽  
Francine Battaglia
Keyword(s):  
Natural Ventilation ◽  
Velocity Ratio ◽  
Thermal Conditions ◽  
Ambient Air ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Solar Chimney ◽  
Window Position ◽  
Pi Theorem

A solar chimney is a natural ventilation technique that has a potential to save energy consumption as well as to maintain the air quality in the building. However, studies of buildings are often challenging due to their large sizes. The objective of the current study was to determine relationships between small- and full-scale solar chimney system models. In the current work, computational fluid dynamics (CFD) was utilized to model different building sizes with a solar chimney system, where the computational model was validated with the experimental study of Mathur et al. The window, which controls entrainment of ambient air, was also studied to determine the effects of window position. Correlations for average velocity ratio and non-dimensional temperature were consistent regardless of window position. Buckingham pi theorem was employed to further non-dimensionalize the important variables. Regression analysis was conducted to develop a mathematical model to predict a relationship among all of the variables, where the model agreed well with simulation results with an error of 2.33%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model.

Evaluation of a Small and Fast Planing Boat’s Seakeeping Performance at the Design Stage

2015 ◽  
Author(s):  
Dong Jin Kim ◽  
Sun Young Kim
Keyword(s):  
Model Tests ◽  
Full Scale ◽  
Scale Model ◽  
Design Stage ◽  
Small Scale ◽  
Irregular Wave ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Scale Ratio ◽  
Free Running

Seakeeping performance of a planing boat should be sufficiently considered and evaluated at the design stage for its safe running in rough seas. Model tests in seakeeping model basins are often performed to predict the performance of full-scale planing boats. But, there are many limitations of tank size and wave maker capacity, in particular, for fast small planing boats due to small scale ratio and high Froude numbers of their scale models. In this research, scale model tests are tried in various test conditions, and results are summarized and analyzed to predict a 3 ton-class fast small planing boats designed. In a long and narrow tank, towing tests for a bare hull model are performed with regular head waves and long crested irregular head waves. Motion RAOs are derived from irregular wave tests, and they are in good agreements with RAOs in regular waves. Next, model ships with one water-jet propulsion system are built, and free running model tests are performed in ocean basins. Wave conditions such as significant heights, modal periods, and directions are varied for the free running tests. Motion RMS values, and RAOs are obtained through statistical approaches. They are compared with the results in captive tests for the bare hull model, and are used to predict the full-scale boat performances.

Numerical Investigation on the Plastic Response of a Small-Scale Laterally Impacted Tanker Double Hull Structure

2012 ◽  
Author(s):  
Richard Villavicencio ◽  
Young-Hun Kim ◽  
Sang-Rai Cho ◽  
C. Guedes Soares
Keyword(s):  
Dynamic Response ◽  
Strain Rate ◽  
Scaling Laws ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Plastic Response ◽  
Hull Structure ◽  
Double Hull ◽  
The Impact

Numerical simulations are presented, on the dynamic response of a one-tenth scaled tanker double hull structure struck laterally by a knife edge indenter. The small stiffeners of the full-scale prototype are smeared in the small-scale model by increasing the thicknesses of the corresponding plates. The dynamic response is evaluated at an impact velocity of 7.22 m/s and the impact point is chosen between two frames to assure damage to the outer shell plating and stringers. The simulations are performed by LS-DYNA finite element solver. They aim at evaluating the influence of strain hardening and strain rate hardening on the global impact response of the structure, following different models proposed in the literature. Moreover, the numerical model is scaled to its full-scale prototype, summarizing the governing scaling laws for collision analysis and evaluating the effect of the material strain rate on the plastic response of large scaled numerical models.

scholarly journals DISPLACEMENTS OF SIDE WALLS WITH WALL-GIRTS IN INDUSTRIAL BUILDINGS UNDER VERTICAL SETTLEMENTS

2021 ◽  
Vol 30 (1) ◽  
Author(s):  
Noemí M. Subelza ◽  
Verónica A. Pedrozo ◽  
Rossana C. Jaca ◽  
Luis A. Godoy
Keyword(s):  
Computer Modelling ◽  
Computational Modelling ◽  
Full Scale ◽  
Scale Model ◽  
Design Stage ◽  
Small Scale ◽  
Industrial Buildings ◽  
Out Of Plane ◽  
Side Walls ◽  
Lateral Displacements

The localized settlement of columns in large metal industrial buildings induces out-of-plane displacements of side walls of the same order as the settlement, which may affect service conditions in the building. For a structural configuration formed by frames, side-walls and wall-girts, this work reports results from testing a small-scale model together with computational modelling of the full-scale structure. Dimensional analysis was used to scale the geometry and properties from full-scale to small-scale, leading to an overall scale factor of 1:15. Differential settlements having a controlled amplitude were imposed at the central column, and displacements were monitored using mechanical devices. The computational model employed shell elements for side-walls and wall- girts. Good agreement was found between tests and computer modelling. The results at the full- scale level, indicate that, for settlements likely to occur in granular soils, the associated lateral displacements exceed those allowed by current US regulations. Stiffening the structure was investigated by use of stiffer girts, as well as by reducing their spacing. The influence of frame height was also investigated. The overall conclusion is that out-of-plane displacements of side- walls may easily exceed allowable values unless they are specifically considered at a design stage.

Evaluation of CCHE2D hydrodynamic and sediment transport model to simulate erosional sources in row crop agriculture in Midwest US

2020 ◽  
Author(s):  
Robert Wells ◽  
Yafei Jia ◽  
Henrique Momm ◽  
Carlos Castillo ◽  
Dalmo Vieira ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Soil Loss ◽  
Transport Model ◽  
Landscape Evolution ◽  
Small Scale ◽  
Agricultural Fields ◽  
Data Set ◽  
Sediment Transport Model ◽  
Total Soil ◽  
Physically Based

<p>Soil erosion due to rainfall and overland flow can be detrimental to agricultural management and long-term agricultural sustainability. Although numerous conservation measures and planning strategies have greatly reduced the amount of sediment moving within the landscape, there are still unresolved questions concerning initiation of particle motion, susceptibility to erosion, total soil loss, sediment transport and general measurement theory. Within agricultural fields, ephemeral erosion is particularly harmful because these sources can accelerate sediment transport, often yield more sediment than interrill sources and are more challenging to mitigate. In this study, terrain data were collected by aerial photogrammetry using an unmanned aerial system (UAS) following planting and approximately one month later, while climate variables during the period were collected using NexRad radar. Imagery was captured within seven agricultural fields (six in Iowa and one in Minnesota), ranging in size from 0.6 to 3.6 hectare (1.6 to 8.8 acre). Considering the small scale in topographic variation between two surveys, extreme efforts were applied to image processing and geospatial registration. Advanced models for camera calibration utilizing Micmac open-source photogrammetry software package were used to account for complex distortion patterns in the raw image data set. The undistorted images were then processed using Agisoft Photoscan for camera alignment, model georeferencing and dense point cloud generation (millions to billions of points per survey), from which digital elevation models (DEMs; 10 to 57 million cells) were produced. A physically-based finite element hydrodynamic and sediment transport model (CCHE2D, developed at the National Center for Computational Hydroscience and Engineering) was applied to simulate hydrological (runoff), sediment detachment (raindrop splash, sheet flow, and concentrated flow erosion) and sediment transport/deposition landscape evolution processes. Simulated geomorphological and sediment budget results over time were compared to field observations for model input parameter adjustment and consequently quantification of estimates. Integration of high-resolution spatial and temporal topographic measurements with physically-based numerical models support the development and validation of dynamic landscape evolution models needed for accurate prediction and quantification of gully initiation, evolution and impact on total soil loss and effective conservation management planning.</p>

Rotor Scale Model Tests for Power Conversion Unit of GT-MHR

2008 ◽  
Author(s):  
C. B. Baxi ◽  
N. G. Kodochigov ◽  
S. E. Belov ◽  
M. N. Borovkov
Keyword(s):  
Power Conversion ◽  
Model Tests ◽  
Suspension System ◽  
Full Scale ◽  
Magnetic Bearings ◽  
Scale Model ◽  
Small Scale ◽  
Conversion Unit ◽  
Electro Magnetic ◽  
Rotor Model

A power-generating unit with the high-temperature helium reactor (GT-MHR) has a turbomachine (TM) that is intended for both conversion of coolant thermal energy into electric power in the direct gas-turbine cycle, and provision of helium circulation in the primary circuit. The vertically oriented TM is placed in the central area of the power conversion unit (PCU). TM consists of a turbocompressor (TC) and a generator. Their rotors are joined with a diaphragm coupling and supported by electro-magnetic bearings (EMB). The complexity and novelty of the task of the full electromagnetic suspension system development requires thorough stepwise experimental work, from small-scale physical models to full-scale specimen. On this purpose, the following is planned within the framework of the GT-MHR Project: investigations of the “flexible” rotor small-scale mockup with electro-magnetic bearings (“Minimockup” test facility); tests of the radial EMB; tests of the position sensors; tests of the TM rotor scale model; tests of the TM catcher bearings (CB) friction pairs; tests of the CB mockups; tests of EMB and CB pilot samples and investigation of the full-scale electromagnetic suspension system as a part of full-scale turbocompressor tests. The rotor scale model (RSM) tests aim at investigation of dynamics of rotor supported by electromagnetic bearings to validate GT-MHR turbomachine serviceability. Like the full-scale turbomachine rotor, the RSM consist of two parts: the generator rotor model and the turbocompressor rotor model that are joined with a coupling. Both flexible and rigid coupling options are tested. Each rotor is supported by one axial and two radial EMBs. The rotor is arranged vertically. The RSM rotor length is 10.54 m, and mass is 1171 kg. The designs of physical model elements, namely of the turbine, compressors, generator and exciter, are simplified and performed with account of rigid characteristics, which are identical to those of the full-scale turbomachine elements.

scholarly journals Prediction of Seabed Scour Induced by Full-Scale Darrieus-Type Tidal Current Turbine

2019 ◽  
Vol 7 (10) ◽  
pp. 342 ◽  
Author(s):  
Sun ◽  
Lam ◽  
Dai ◽  
Hamill
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Tidal Current ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Scour Depth ◽  
Equilibrium Scour Depth ◽  
Tidal Current Turbine ◽  
Current Turbine

Scour induced by a Darrieus-type tidal current turbine was investigated by using a joint numerical and experimental method with emphasis on the scour process of a full-scale turbine. This work proposes a new numerical method to estimate turbine scour developments, followed by model validation through experimental data in the initial stage. The small-scale numerical model was further extended to a full-scale model for the prediction of turbine scour. The numerical model consists of (1) k-ω turbulence closure, (2) a sediment transport model, and (3) a sediment slide model. The transient-state model was coupled with a morphologic model to calculate scour development. A dynamic mesh updating technique was implemented, enabling the autoupdate of data for the grid nodes of the seabed at each time step. Comparisons between the numerical results and the experimental measurements showed that the proposed model was able to capture the main features of the scour process. However, the numerical model underestimated about 15%–20% of the equilibrium scour depth than experimental data. An investigation of the temporal and spatial development of seabed scour around a full-scale Darrieus-type tidal current turbine is demonstrated. This work concludes that the proposed numerical model can effectively predict the scour process of tidal current turbines, and the rotating rotor has a significant impact on the equilibrium scour depth for full-scale turbines.

Steady-State Natural Convection in Empty and Partitioned Enclosures at High Rayleigh Numbers

1990 ◽  
Vol 112 (3) ◽  
pp. 640-647 ◽  
Author(s):  
D. A. Olson ◽  
L. R. Glicksman ◽  
H. M. Ferm
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Radiation Heat Transfer ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Different Temperatures ◽  
Rayleigh Numbers ◽  
Vertical Partition

Steady-state natural convection, which occurs in building enclosures (Rayleigh numbers of 1010), was studied experimentally in a full-scale room and in a 1:5.5 small-scale physical model containing R114 gas. The model was geometrically similar, had the same Rayleigh number, and had the same dimensionless end wall temperatures as the full-scale room. Configurations were tested with the enclosure empty, with a vertical partition extending from the floor to midheight, and with the vertical partition raised slightly off the floor. For isothermal opposing end walls at different temperatures, excellent agreement was found between the full-scale room and the scale model in flow patterns, velocity levels, temperature distributions, and heat transfer, even though the radiation heat transfer was not scaled between the two models.

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