Hydraulic calculations of a water curtain as a pipeline with cocurrent flow

Summary

The need for water curtains arises at over load of any toxic and explosive liquids and gases; and with account for the continuous growth of overload amounts owing to the construction of new terminals it is necessary to design water curtains more and more often. The analysis of hydraulic calculations of a water curtain in a distribution pipeline is presented. When calculating through nozzles the expediency of using the widely known flow rate coefficient instead of an unknown departmental coefficient is shown. At present formulas for calculating the total flow through the water curtain nozzles and head loss in a distribution pipeline are lacking. The method of calculating such a pipeline (pipeline with concurrent flow) is known from the hydraulics. However, it cannot be used because it is suitable for the constant specific flow rate, and the specific flow rate of the water curtain is not constant. The task of making hydraulic calculations of a water curtain for a distribution pipeline has been formulated as follows: determining such pressure and flow rate values that provide for the set flow and pressure for the last (most remote) nozzle is required. When determining head losses in a distribution pipeline the flow rate value before the pipeline multiplied by the decreasing coefficient is used. It was stated that this coefficient depended on the ratio of the diameter of the distribution pipeline to the nozzle diameter. The diagram and formula describing the above-noted dependency are presented together with an example of the calculations illustrating the use of the obtained dependencies.

Key words

hydraulic design , pressure losses , firefighting water system , water curtain , distribution pipeline , flow coefficient

Hydraulic calculation of dissipating outfalls

Summary

Recently, significant attention has been paid to the environmental issues in the reconstruction, upgrade, and construction of wastewater treatment facilities in the Russian Federation. In these instances, estimating the capacity (performance) of the final element in the treatment system, i. e. the discharge of effluents into a water body is obligatory. Calculating dissipating outfalls presents certain challenges, since this issue has received insufficient attention so far. Making hydraulic calculations of a dissipating outfall is proposed as not a calculation of one single element – the head – but of the entire system, i. e. supply and distribution pipelines, and all the existing heads (openings). Addressing this problem lies in solving a system of algebraic nonlinear equations describing flow distribution with variable withdrawal rates in the dissipating outfall under consideration. Consequently, the discharge rates through each head and the piezometric head values at all the outfall assemblies are determined. The proposed mathematical model of a dissipating outfall provides for not only estimating the functionality of an existing or planned outfall but also, in case of a damage (rupture) in the underwater part of the outfall, determining its parameters, i. e. the orifice area and the rate of the flow entering the watercourse through it. By analogy with pumps, the concept of a head and rate specification is introduced, providing for the use of one parameter (flow rate or head at the initial outfall assembly) to determine the other parameter eliminating the hydraulic calculation of the entire outfall. An example of a hydraulic calculation of a dissipating outfall with an estimation of the operating parameters is provided.

Key words

hydraulic design , pressure losses , distribution pipeline , headwall , variable abstraction , effluent discharge into a water body , dissipating outfall