Recent Advances in Hydraulic Physical Modelling

ISBN-13: 9780792301967 / Angielski / Twarda / 1989 / 627 str.

Rui Martins

Opis

The growing use of mathematical models in hydraulics has not made physical models obsolete. They keep pace with mathematical models and in some cases make progress in conjunction with them Physical models continue to be developed: more precise use of similitude criteria, better knowledge of scale effects, new and more complex types of model, use of various artifices, more ade quate instrumentation, automation of the operation of model- all these pOint to that development. What was needed was to make a survey of the situation, and this was the principal aim of the NATO Advanced Study Institute on Recent Advances in Hydraulic Physical Modelling, which took place on the premises of the Laborat6rio Nacional de Engenharia Civil (LNEC) in Lisbon, Portugal, from 4th to 15th July 1988, and of which this book is one of the main outputs. It is divided into 11 chapters, corresponding to 28 lectures that cover five areas: fundamentals of physical modelling, river models, hydraulics of structures, maritime hvdraulics and densi ty models. -- Hodelling is obviously dependent on the knowledge of the phe nomena that are being modelled. This book is therefore also a book on hydraulic engineering in general and not only on phv sical, modelling. The text also refers to mathematical modelling, experimental methods in hydraulics and observation of nature and prototypes.

Spis treści

1 Fundamentals of Hydraulic Physical Modelling.- 1. Introduction.- 2. Principles of the Theory of Dimensions.- 2.1. Dimensional and dimensionless quantities.- 2.2. Characteristic parameters.- 2.3. Dimensionless expression of a natural law.- 3. Principles of the Theory of Similarity.- 3.1. The idea of a model.- 3.2. Definition of dynamic similarity.- 3.3. Dynamically similar models and their scales.- 4. Hydraulic Models.- 4.1. General, conventional models (operating with water).- 4.2. Distortion.- 4.3. Froudian models.- 5. Further Approaches to Hydraulic Model Design.- 5.1. General.- 5.2. Examples.- 5.2.1. Inception of sediment transport.- 5.2.2. OTEC — Power plants (Ref. [9]).- 5.2.3. River flow with bed covered by sand waves.- 2 River Models.- 1. Non Maritime Models with Fixed Bed.- 1.1. Similarity for rivers and open channels.- 1.1.1. Undistorted models.- 1.1.2. Distorted models.- 1.2. Models of hydraulic structures.- 1.2.1. Similarity.- 1.2.2. Examples of hydraulic structures.- 1.2.2.1. Low-head hydraulic structures.- 1.2.2.2. Flood-discharge structures (weirs and spillways).- 1.2.2.3. Internal flow systems.- 1.2.3. Problems connected to air entrainment.- 1.2.3.1. Two-phase flow.- 1.2.3.2. Vortices.- 1.3. Mixing models.- 1.3.1. Turbulent entrainment at the effluent jet.- 1.3.2. Rise of the jet by buoyancy.- 1.3.3. Convective spread over the surface.- 1.3.4. Mass transport.- 1.3.5. Diffusion and dispersion.- 1.3.6. Loss of heat through surface.- 1.4. Models of flows without a free surface.- 1.5. Models of river training schemes.- 1.6. Model techniques.- 1.6.1. Construction.- 1.6.2. Control and operation.- 1.6.3. Calibration.- 1.6.4. Measurement and instrumentation.- 1.6.4.1. Flow velocities.- 1.6.4.2. Water levels.- 1.6.4.3. Water pressures.- 2. Sediment Transport in Rivers.- 2.1. Basic concepts and relevant parameters.- 2.1.1. The granular material.- 2.1.2. The flow: velocity distribution.- 2.1.2.1. Laminar zone y < ?.- 2.1.2.2. Turbulent zone y > ?.- 2.1.3. Dimensional analysis of the two-phase phenomenon.- 2.2. Beginning of sediment transport — transport rate.- 2.3. Sand waves.- 2.3.1. If the flow is tranquil (Fr < 1).- 2.3.2. In the upper regime (Fr > 1).- 2.4. Friction factor.- 2.5. Suspended load.- 3. River Models with Movable Bed.- 3.1. Model laws for bedload.- 3.1.1. Models with flat bed.- 3.1.2. Models with sand waves.- 3.1.2.1. Scaling of undistorted models.- 3.1.2.2. Scaling of distorted models.- 3.2. Modelling techniques.- 3.2.1. Construction.- 3.2.2. Choice of movable bed material.- 3.2.3. Calibration of the model.- 3.2.4. Operation and measurement.- 3.3. Case studies.- 3.3.1. The Rhône river near the confluence with the Drôme river.- 3.3.2. The Loire river near Orleans in France.- 3.4. Comparison with other modelling techniques.- 3.4.1. Aerodynamic models.- 3.4.2. Numerical models.- 3 Models for Study of the Dynamic Behaviour of Structures in Flow and Waves.- 1. Introduction in the Held of Hydro-Elasticity.- 2. The Single Resonator in a Flow Field.- 3. Response Calculations at Random Excitation.- 4. Introduction to Added Mass, Added Damping, Added Rigidity and Self-Excitation.- 4.1. Introduction.- 4.2. Introduction of added mass, added damping and added rigidity.- 4.3. Self-exciting vibrations of gates.- 4.4. The bathing plug equations.- 4.5. Application of theory to underflow type of gates.- 5. Models with Elastic Similarity for the Investigation of Hydraulic Structures.- 5.1. Hydraulic reproduction laws.- 5.2. Elastic properties of models.- 5.3. Combination for flow without free liquid surface.- 5.4. Combination for flow with free liquid surface.- 5.5. Model research and verification measurement on the Hagestein visor gates.- 5.6. Further application of elastic similarity models.- 6. The Use (Applicability and Limitations) of Physical Models in Vibration Research.- 6.1. Introduction.- 6.2. Types of physical models for vibration research.- 6.3. Air models for gate research.- 6.4. General remarks on the reliability of models.- 6.5. Particular scale effects of models with continuous elasticity.- 7. Interpretation of Results.- 8. Cavitation Research.- 9. Strategy for Vibrations-Free Design of Larger Gate Structures.- 10. New Developments in the Field of Modelling Hydro-Elasticity.- 4 Models for Study of the Hydrodynamic Actions on Hydraulic Structures.- 1. Introduction.- 1.1. General considerations.- 1.2. Formulation of the problem.- 2. Hydrodynamic Actions on Stilling Basins.- 2.1. General aspects.- 2.2. Theory and procedures for physical modelling of hydrodynamic actions.- 2.3. Evaluation of hydrodynamic actions on stilling basins.- 2.3.1. Method of global behaviour.- 2.3.2. Method based on direct measurement of F (t).- 2.3.3. Evaluation of hydrodynamic forces and moments by means of surface pressure measurements.- 2.3.3.1. General aspects.- 2.3.3.2. Evaluation of hydrodynamic actions.- 3. Dynamic Analysis.- 3.1. General considerations.- 3.2. Case studies.- 4. Hydraulic Modelling of Hydrodynamic Actions.- 4.1. Formulation of the problem. Similarity laws.- 4.2. Air entrainment on chutes and overflow spillways.- 4.3. Mean pressures on ski jumps.- 4.4. Free falling turbulent jets through the atmosphere.- 4.5. Diffusion of plunging turbulent jets in a pool. Effects on the dynamic pressures.- 4.6. Statistical parameters of pressure field. Scale effects.- 5 Density Models.- 1. Introduction.- 1.1. Definition.- 1.2. Historical background.- 1.3. Unique aspects.- 1.4. Advantages of physical models.- 1.5. Scope of paper.- 2. Modelling Principles.- 2.1. General.- 2.2. Similitude requirements.- 3. Scale and Boundary Effects.- 3.1. Definition of scale effects.- 3.2. Minimizing scale effects.- 3.3. Boundary effects.- 3.4. Procedures.- 3.4.1. Cooling tower studies.- 3.4.2. Dense gas releases.- 3.5. Use of stratified flow flumes.- 4. Limitations.- 4.1. Physical understanding.- 4.2. Multiple flow regime conflicts.- 4.3. Model restrictions.- 4.4. Model costs.- 5. Model Specifications.- 5.1. Scale.- 5.2. Boundary conditions.- 5.3. Characteristics of receiving waters.- 5.4. Characteristics of effluent.- 5.5. Test procedures.- 5.6. Sensitivity tests.- 5.7. Calibration.- 6. Applications.- 6.1. Outfalls.- 6.2. Estuary models.- 6.3. Density current models.- 6.4. Reservoir/cooling pond models.- 6.5. Accidental release models.- 6.6. Cooling tower models.- 6.7. Porous media models.- 6.8. Internal waves models.- 6.9. Sedimentation models.- 6.10. Other models.- 7. Case Studies.- 7.1. Diablo canyon model studies.- 7.2. Tailings discharge studies.- 7.3. Buoyant discharges into stagnant rivers.- 6 Tidal Models.- 1. Introduction.- 1.1. General.- 1.2. Fundamentals of tidal motion.- 2. Model Laws.- 2.1. General.- 2.2. Fixed bed models.- 2.3. Movable bed models.- 2.4. Wave-current interaction.- 3. Boundary Conditions.- 4. Operation of Tidal Models.- 4.1. General.- 4.2. Tide generation.- 4.3. Currents. Fluvial discharges.- 4.4. Model sediments.- 4.5. Calibration.- 4.5.1. Fixed bed models.- 4.5.2. Movable-bed models.- 5. Instrumentation. Data Acquisition and Model Control.- 5.1. General.- 5.2. Data acquisition.- 5.2.1. Tidal levels.- 5.2.2. Currents.- 5.2.3. Bottom surveying.- 5.3. Data analysis.- 5.4. Automatic control.- 5.4.1. The control unit.- 5.4.2. Control of operation instruments.- 5.4.3. Data acquisition.- 5.4.4. The need for instrument calibration.- 6. Case Studies.- 7 Hybrid Modelling as Applied to Hydrodynamic Research and Testing.- 1. Introduction.- 2. The Design of the Demonstration Hybrid Model.- 2.1. The mathematical model of the entire estuary.- 2.2. The structure of the control interval.- 2.3. The hybrid model simulation.- 2.3.1. Variation of the control interval.- 2.3.2. Application of Q-values.- 2.3.3. The effect of noise and cross-modes.- 3. The Construction of the Demonstration Hybrid Model.- 3.1. The physical model and the hybrid interface.- 3.2. Instrumentation and calibration.- 3.2.1. Water level gauges.- 3.2.2. Velocity paddle meters.- 3.2.3. Pump calibration.- 3.3. The physical model calibration.- 4. Experimentation with the Hybrid Model.- 4.1. Variation of the control interval.- 4.2. Effect of the variation of AvH.- 4.3. Delay of transfer of Q-control.- 4.4. Basic performance tests of the system.- 5. Other Tidal Control Machines.- 6. Future Plans.- 6.1. Extension to 2 D-schemes.- 6.2. Array processors and massively parallel processors.- 7. Hybrid Applications.- 7.1. The St. Lawrence estuary model.- 7.2. The bay of Fundy hybrid model.- 7.3. The Senegal hybrid model.- 7.4. The Ocean Ranger wind simulation.- 7.5. Remote control of a service vessel.- 7.6. Tidal power turbines.- 7.7. Wave generation.- 8. Future Aspects of Hybrid Modelling and Conclusions.- 8 Wave Grouping and Harbour Design. Safe Underkeel Allowances for Vessels in Restricted Depths.- I.- 1. Introduction.- 2. Real Sea Measurements.- 3. Random Wave Model.- 4. Real Time Set-Down Compensation.- 5. Experimental Results.- 6. Application to a Physical Model.- 7. Conclusions.- II.- 1. Introduction.- 2. Background to the Dover Strait Study.- 3. Acceptable Risk Factor.- 4. Wave Climate in the Dover Strait.- 4.1. Storm wave predictions.- 4.2. Swell predictions.- 5. Ship Responses in Waves.- 5.1. Computer model.- 5.2. Physical model.- 5.3. Comparison of physical and computer model results.- 5.4. Set-down allowance.- 6. Water Depth Uncertainties.- 6.1. Surveying errors.- 6.2. Sea bed mobility.- 6.3. Draught uncertainties.- 6.4. Combined depth uncertainty.- 6.5. Negative storm surges.- 7. Vessel Squat.- 8. Calculation of Underkeel Allowances.- 9. Conclusions.- 9.1. NE bound route.- 9.2. SW bound route.- 9.3. General points.- 9 Sea Wave Simulation.- 1. Introduction.- 2. Sea Wave Characterization.- 2.1. Introduction.- 2.2. Wave height and period distribution.- 2.3. The spectrum.- 2.4. Wave groups.- 2.4.1. Introduction.- 2.4.2. The envelope method.- 2.4.3. The SIWEH method.- 2.4.4. Relationship between the two approaches.- 3. Computer Simulation.- 3.1. Introduction.- 3.2. Spectrum specified.- 3.2.1. Random phase method.- 3.2.2. Digital filtering digital white noise.- 3.2.3. ARMA methods.- 3.3. Spectrum and wave grouping specified.- (1) through SIWEH.- (2) through GF.- (3) through a given record.- (4) through Wr.- 4. Physical Model Simulation.- 4.1. Introduction.- 4.2. Spectrum specified only.- 4.2.1. Electronically filtering electronic white noise.- 4.2.2. Previous computer synthesis of a time series.- 4.3. Record specified.- 4.3.1. Introduction.- 4.3.2. Method of integration of the horizontal velocity.- 4.3.3. Filter theory method.- 4.3.4. Fourier decomposition method (DM).- 4.4. Spectrum and wave grouping specified.- 4.5. Separation of incident and reflected waves.- 5. Topics on Multidirectional Simulation.- 5.1. Introduction.- 5.2. Directional analysis.- 5.3. Computer simulation.- 5.4. Physical model simulation.- 6. “Deterministic” and “Non-Deterministic” Simulation.- 10 Dynamic Actions on Breakwaters (Rubble-Mound and Caisson/Composite Type Breakwaters).- 1. Rubble-Mound Breakwaters.- 1.1. Introduction.- 1.2. Hydraulic model testing in wave flumes using irregular waves.- 1.3. Stability of breakwater armour layers.- 1.3.1. Wave period influence.- 1.4. Scatter in breakwater stability.- 1.5. Status on scale effects in breakwater modeling.- 1.6. Evaluation of scale effects in hydraulic models by analysis of laminar and turbulent flows.- 1.6.1. Introduction.- 1.6.2. Flow through granular material.- 1.6.3. Limits for laminar and turbulent flow.- 1.6.4. Compensation for scale effects.- 1.6.5. Energy dissipation in models.- 1.7. Results of model tests on 2-D breakwater structure.- 1.7.1. Force measurements.- 1.7.2. Wave forces on a two-dimensional breakwater.- 1.7.3. Test results.- 1.7.4. Jonswap spectrum.- 1.7.5. Wave slamming on armour units.- 1.8. Dynamic forces on breakwater superstructures.- 1.8.1. Introduction.- 1.8.2. Problems relating to design of superstructures.- 1.8.3. Physics of wave forces on superstructures.- 1.8.4. Forces on the front face.- 1.8.5. Forces under the base.- 1.8.6. Model laws.- 1.8.7. Parameters influencing wave forces on superstructures.- 1.8.8. Examples of results of model experiments.- 1.9. Wave overtopping on breakwaters.- 1.9.1. Introduction.- 1.9.2. Physics of wave “spray-carry-over” and overtopping.- 1.9.3. Prototype measurements.- 1.9.4. Model test results. Presentation of results.- 1.9.5. Test equipment and procedure.- 1.9.6. Horizontal distribution of overtopping.- 1.9.7. Distribution of wave overtopping discharge of individual waves.- 1.9.8. Criteria for acceptable overtopping.- 2. Caisson/Composite Breakwaters.- 2.1. Introduction.- 2.2. Wave forces on caisson type structures.- 2.3. Dynamics of shock forces on vertical face breakwaters.- 2.4. Compression model law.- 2.5. Statistical analysis of wave forces.- 2.6. Wave force determination in physical model.- 2.6.1. Example of wave forces on caisson.- 2.6.2. Presentation of test results.- 2.7. Forces on protruding parapets.- 2.8. Overtopping on caisson breakwater with sloping face.- 2.9. Stability of rubble foundation for composite breakwaters.- 2.9.1. Introduction.- 2.9.2. Considerations concerning stability.- 2.9.3. Comparison with pure standing waves.- 2.9.4. Stability formula.- 2.9.5. Test equipment and procedures.- 2.9.6. Influence of wave height, wave period and depth of foundation.- 2.9.7. Influence of sloping face of the caisson above SWL.- 11 Physical Modelling of Littoral Processes.- 1. Abstract.- 2. Introduction.- 3. Coastal Processes-An Overview.- 3.1. Alongshore transport.- 3.2. Cross-shore transport.- 4. Modelling Facilities.- 4.1. Wavemakers.- 4.2. Wave tanks and basins.- 5. Hydrodynamic Physical Models.- 6. Littoral Process Models.- 6.1. Model laws.- 6.2. Beach profile modeling.- 6.3. Coastal models.- 7. Model Testing Procedures.- 8. Conclusion.- Final Remarks.- Annexes.- Annex 1 — Introductory words.- Annex 2 — Panel sessions/round tables.- Annex 3 — Non-usual hydraulic models.- Annex 4 — Higher order wave generation in laboratory experiments.- Annex 5 — List of participants.