Determining Critical Submergence in Tanks by Means of Reynolds & Weber Numbers

Critical submergence in pumping systems can be determined using a number of calculations, all of which result from heterogeneous geometries based on water. The most widely spread critical submergence formula is that of the Hydraulic Institute. A study, carried out in Germany, looked at eight different formulations used to calculate critical submergence, comparing their results with those of a hydraulic model test. The conclusion is that the simplest models, overestimate the critical submergence. Similarly, a study of submergence in water intake structures concluded that predicted values were much higher than real values. A detailed analysis has been done to detect the origin of the off-set between the measured submergence and the calculated value. The main aspects selected from the analysis were the fluid properties involved in the surface deformation and the dynamic behavior outlet flow, so two a-dimensional numbers have been selected, Weber and Reynolds. To build an equation, to calculate the critical submergence, based on the mentioned a-dimensional numbers, a mixed technique (numerical and testing) has been used. The first step was driving a test in a hydraulic model to verify the critical submergence level. Then, a numerical model was built to simulate the same phenomenon and calibrate it, to be used in the future. After that, the second step is to simulate and calculate the critical submergence with other boundary condition (fluid, flow rate, pipe diameter). Once the critical submergence is calculated, a non-linear least squared approach has been developed to build the equation to calculate the critical submergence based on the Reynolds and Weber number. The numerical method used in this paper is a finite element model with a fluid volume scheme, used normally in the fluid simulation activities.

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Conflicts of Interest

The authors declare no conflicts of interest.

Cite this paper

Moreno, C. (2014) Determining Critical Submergence in Tanks by Means of Reynolds & Weber Numbers. World Journal of Engineering and Technology, 2, 222-233. doi: 10.4236/wjet.2014.23024.

 [1] Hydraulic Institute (1998) American National Standard for Pump Intake Design. ANSI, New York. [2] Prosser, M.J. (1977) The Hydraulic Design of Pump Sumps and Intakes. British Hydromechanics Research Association/Construction Industry Research & Information Association. [3] Padmanabhan, M. and Hecker, G.E. (1984) Scale Effects in Pump Sump Models. Journal of Hydraulic Engineering, 110, 1540-1556. http://dx.doi.org/10.1061/(ASCE)0733-9429(1984)110:11(1540) [4] Knauss, J. (1987) Swirling Flow Problems at Intakes. Hydraulic Structures Design Manual, 1AA, Balkema, Rotterdam. [5] Flygt (2002) Design Recommendations for Pumping Stations with Dry Installed Submersible Pumps. Flygt, Stockholm. [6] Werth, D. and Frizzell, C. (2009). Minimum Pump Submergence to Prevent Surface Vortex Formation. Journal of Hydraulic Research, 47, 142-144. http://dx.doi.org/10.3826/jhr.2009.2699 [7] Kleynhans, S.H. (2012) Physical Hydraulic Model Investigation of Critical Submergence for Raised Pump Intakes. Stellenbosch University, Stellenbosch. [8] Swaroop, R. (1973) Vortex Formation at Intakes. ME Dissertation, University of Roorkee, Roorkee. [9] Ansar, M. and Nakato, T. (2001) Experimental Study of 3D Pump-Intake Flows with and without Cross Flow. Journal of Hydraulic Engineering, 127, 825-834. http://dx.doi.org/10.1061/(ASCE)0733-9429(2001)127:10(825) [10] Hundley, K. (2012) Modelling of a Pump Intake with a Single Phase CFD Model. Stellenbosch University, Stellenbosch. [11] Ahmad, Z., et al. (2004) Critical Submergence for Horizontal Intakes in open Channels Flows. Dam Engineering, 19, 71-90. [12] Tomoyoshi, O. and Kyoji, K. (2005) CFD Simulation of Flow in Model Pump Sumps for Detection of Vortices. 8th Asian International Fluid Conference, 12-15 October 2005, Yichang, 14.