5.9.5. Modular Outlets Most of the modular outlets have moving parts which make them costly to install as well as maintain. The following two types of modular outlets (also known as rigid modules), however, do not have any moving part:
(i) Gibb’s rigid module, and (ii) Khanna’s rigid module.
5.9.5.1. Gibb’s Rigid Module This module has an inlet pipe under the distributary bank. This pipe takes water from distributary to a rising spiral pipe which joins the eddy chamber (Fig. 5.8). This arrangement results in free vortex motion. Due to this free vortex motion, there is heading up of water (owing to smaller velocity at larger radius–a characteristic of vortex motion) near the outer wall of the rising pipe. The water surface thus slopes towards the inner wall. A number of baffle plates of suitable size are suspended from the roof of the eddy chamber such that the lower ends of these plates slope against the flow direction. With the increase in head, the water banks up at the outer wall of the eddy chamber and impinges against the baffles and spins round in the compartment between two successive baffle plates. This causes dissipation of excess energy and results in constant discharge. The outlet is relatively more costly and its sediment withdrawal is also not good.
