The Use of Mini- and Micro-Models to Solve Some Type of Problems

The use of micro-or mini-models to solve some types of hydraulic problems is a subject that it is not entirely settled. It seems that for some type of problems these models can provide useful, economic and timely information. An introduction to this kind of models and two examples whose results were deemed useful are presented in this paper and some recommendations follow. First example: In spillway design the knowledge of the scouring processes downstream the flip bucket of a spillway is very important. A study on the scouring of the bed material downstream the flip bucket, with data from the Penitas Dam (Mexico), was carried out for a non-distorted, movable bed mini-model with a length scale of 1: 759 for three different discharges and seven different materials. The objective of the essays was to evaluate the predictive capacity of the mini-model and to propose and calibrate a formula to predict the geometry and maximum scour produced by the water. Experimental results show that the feasibility of this kind of models appears to be justified. The proposal is to use mini-models with scales of 1: 500 to 1: 1000 in tests with half-hour duration, as a substitute of the rather expensive and long duration tests that are presently used. Second example: In small ports or marines, it may be necessary to reduce the height of waves at a given zone to protect the boarding of passengers from small sailing vessels. In this case a mini-model can provide sufficient qualitative results to be able to propose the necessary improvements. The results of a National Polytechnic Institute study at Tangolunda Bay (Mexico) for a mini-model with horizontal and vertical scales of 1: 150 and 1: 100, respectively, are included. It can be concluded that the information obtained from mini-models, as the two presented here, in addition to their didactic value, provide at small cost useful information for spillway design and navigation problems.