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Single flap random wavemaker

Single flap random wavemaker

Flap wavemaker

The Edinburgh Designs flap wavemaker is a complete absorbing random wavemaker that includes the paddle, drive motor, control electronics and power supply. The unit is dryback with a fabric sealing gusset supplied in a watertight stainless steel enclosure ready to fit to the end of an existing narrow flume.

Principle

Principle

Principle

The wavemakers are of a flap type, where the flap is a wedge shaped, glass fibre paddle pivoted about its tapered end on a support frame. The flap is dry back and sealed with a rolling fabric gusset seal so the paddle motion only creates waves in the water in front. It is driven by an electric servo-motor via a belt which runs over a curved sector attached to the paddle top. Springs fastened to the end of the belt offset the hydrostatic force. A force transducer senses the wavemaking forces and  an optical encoder measures the paddle position.

Traditionally wavemakers work with a position feedback control system to create waves. This has the disadvantage that the swept volume of the paddle is dependant on the water level in front of the paddle. So the wave height generated is dependant on many factors including the size of any reflected waves from models or poor quality beaches. The Edinburgh Designs wavemaker measures the incoming wave and corrects the paddle motion to absorb it. The resultant wave field is totally predictable even with highly reflective models. Repeatability is better than 1% allowing results from multiple sequential runs to be combined. The force absorption technique uses two reliable transducers well above the waterline. The technique is significantly better than wavegauge absorption because the transducers do not require setting up and frequent recalibration.

Drive system

Flapping action

Flapping motion

Each paddle has an electrical servo motor that drives a belt running over a curved guide on the top of the paddle. The control electronics, power amplifier and power supply are housed in a self -contained robust steel cabinet. Maintenance is simple with all major components easily accessible well above the waterline. Larger flaps use robust brushless AC servomotors.

Dimensions

single paddle

3.5m wide 0.9m hinge depth single paddle

Edinburgh Designs has built many different-sized single flap wavemakers from 300 to 3500mm wide and hinge to waterline depths of 500 to 1200mm. Many are made to upgrade existing wave tanks so are built to fit the customer's exact requirements.

Tank Layout

It is possible to drop the paddle assembly into a tank but the preferred solution is to use the wavemaker enclosure to form one end of the tank. The absorbing wavemaker creates high quality waves that are stable within a distance equal to three water depths from the paddle face. Valuable research can be conducted in laboratories that are too short for a traditional tank. The paddles can be placed opposing each other at either end of a tank to form an active beach or side by side to control crosswaves. Multiple paddles are controlled by a single computer that can be placed up to 300m from the wavemaker.

Maintenance

Flap wavemakers require no regular maintenance. The drive system consists of regular standard parts and can be replaced by skilled technicians. There are several designs for underwater hinge some designed for maintenance free operation.