Scaling Issues in Hydraulic Modelling

Introduction

The uncertainties involved in many coastal issues and the lack of complete scientific background in some knowledge fields, especially to evaluate extreme coastal-forcing events, the cumulative environmental evolution and impacts on beaches and coastal structures as well as to confirm design procedures, for instance, lead to the need of using physical modelling. There is also little public awareness of the physics behind several coastal processes and physical modelling can help in describing and illustrating them.

In this paper a brief revue on the importance of physical modelling, its advantages in relation to numerical modelling, some basic aspects of physical modelling, related scaling issues and how to control hydraulic modelling and scale effects as well as three case studies and future challenges will be presented.

The Importance of Physical Modelling

Physical models have played a pivotal role in the growth of coastal engineering as a profession . They have given us insight into the complex hydrodynamic regime of the nearshore region, and they have provided us with reliable and economic design solutions to support man’s activities in the coastal zone. Many of our present-day engineering design techniques were developed using laboratory measurements, and numerous theoretical developments have relied on laboratory experiments for validation.
However, many of us can still list some of the limitations of those design approaches, being in some case considered as empirical formulations. This means further tests and measurements are needed to increase the reliability of those formulations, specially performed at scales closer to the prototype, avoiding scale effects and testing new forcing situations. Especially due to climate change and the demand for bigger structures located at higher depths, more accurate design formulations are needed and this will be the most important role of large laboratories of maritime hydraulics. However, as these large tests in large facilities are more expensive they need to work in close relation with other small/medium facilities for preliminary/cheaper analyses.

Physical and numerical modelling tools have developed enormously during the last years. However several issues need still further developments, namely the physics and modelling of sediment transport, the wave-structure interaction analysis and loads determination, erosion and scour near coastal structures as well as medium to long term accurate simulation tools.

From the management side, for instance, plans should be based on an adequate understanding of coastal dynamics. It is necessary to pursue research on many aspects of coastal dynamics in order to better assess and understand erosion and sedimentation problems, predictions of shoreline positions for various scenarios and timescales of climate variability and direct human influence, the vulnerability of beaches, dunes and coastal structures to storms and other extreme events, the impact of artificial coastal structures and ecological changes.

References

The main author of this article is Taveira Pinto, Francisco With contributions by: Paulo Rosa-Santos, Luciana das Neves, Raquel Silva For other articles by this author see Category:Articles by Taveira Pinto, Francisco