Hydrodynamic performance comparison between the outflow of the breakwater oscillating water column (OWC's) devices and offshore OWC device attached to an offshore structure by using Computational Fluid Dynamics (CFD) analysis.

Abstract

The oscillating water column (OWC) Device is a type of wave energy converters (WEC), as it intends to transform energy from wave energy at sea into electricity by using the wave heaving to move confined air and thus drive an air turbine to generate the power. Furthermore, this thesis manages the hydrodynamic analysis of two types of the oscillating water column (OWC) devices that are gliding freely in limited profundity waters and presented in the activity of standard surface waves. The hydrodynamic analysis, the comparison was made by applying the technique of Computational Fluid Dynamics (CFD) analysis. The significant agreement that CFD is an extremely encouraging device that an originator can utilize it to explore and survey gadget survivability under various conditions upon further approvals in different wave conditions, This method provided an efficient tool for complete hydrodynamic analysis of these devices, the hydrodynamic pressure Parameters; and by using the inputs of wave’s characteristics in the Arabian Gulf Area which have an average historical wave height of 1m. The OWC chamber model used in previous experiments has detailed that it is for the breakwater and for the offshore OWC using the inner diameter, which achieves the same cross-sectional area with the breakwater chamber. A numerical model and Numerical Wave Tank (NWT) established to evaluate the interaction of an OWC with the water in different cases of different depths of the sea. ANSYS is used here to find the effects of the water surface in and around the central column, breakwater-mounted OWC, and calculate the equations of Navier-Stokes to get the vertical component of air entering and exiting the vent of the OWC. After modeling and analysis of the output flow, we got to conclusions for the hydrodynamic performance of the breakwater chamber shows higher efficiency than the open ocean fixed OWC, in addition to that the variation of the energy with the wave steepness.Chapter 1.Introduction 1 1.1. Introduction 1 1.2. Forces acting on an OWC 2 1.3. Classification of OWCs by location and shape 3 1.3.1. Location of OWCs 4 1.4. Power take-off for OWC-WEC 7 1.4.1. Rectifying airflow using valves 8 1.4.2. The Wells turbine 8 Chapter 2.Theory behind OWC 11 2.1. Theory 11 2.2. Wave Theoretical Considerations 11 2.3. Wave Small Amplitude Theory 12 2.4. Wave Velocity and Wave Classification 13 2.5. Higher-Order Theories 15 2.5.1. General 15 2.5.2. OWC Efficiency 18 2.6. Research Background 25 Chapter 3.CFD modeling and analysis 26 3.1. Research contents 26 3.2. Research Goals 26 3.3. Modeling and Analysis 27 3.3.1. Numerical Wave Tank 28 3.3.2. Validation of Wave Propagation 37 3.3.3. OWC Numerical Analysis 41 3.3.4. Summarized efficiency equations 43 3.4. Performance of the OWC in a real sea 44 3.4.1. Describing real seas 45 3.4.2. Irregular waves Performance 47 3.4.3. Annual performance 49 3.5. Review of the Modelling 57 3.5.1. Impulse Functions and Mechanical Oscillators 57 3.5.2. Methods of Boundary Element and Diffraction 58 3.5.3. Investigations for Computational Fluid Dynamics 60 3.6. Summary 65 Chapter 4.The Comparative evaluation of analysis results 66 4.1. Hydrodynamics 66 4.1.1. Modeling 66 4.1.2. Major findings 75 4.1.3. Importance 75 4.1.4. Limitations 75 4.2. Time-domain modeling 76 4.2.1. Time-Domain Modeling Main Findings 76 4.2.2. The time-domain modeling Importance 77 4.2.3. Limitations 78 4.3. Computational fluid dynamics 80 4.4. Fluent Results 84 Chapter 5.Discussion 89 5.1. Discussions 89 Chapter 6.Conclusions 95 6.1. Numerical Wave Tank NWT 95 6.2. Parametric Simulations of the OWC 96 6.3. Practical Modeling of the OWC 97 6.4. Limitations 98 Acknowledgment 100 References 100Docto