Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Civil, Construction, and Environmental Engineering


Tube settlers are classified into two configurations; the essentially horizontal and the steeply inclined. Theoretical and experimental studies were conducted on the basis of an extensive literature review to clarify some of the unsettled questions and a model for both design configurations was proposed, the Fadel Model;The model considers the effect of velocity profile variations ranging from uniform at the tube entrance to fully developed laminar flow profiles at the end of the transition length. Three methods for using the model were established: a computer program, design charts, and an equation;The experimental studies demonstrate the validity of the Fadel Model as a design method for determining particle settling length in circular tube settlers. The effect of sludge accumulation on the performance of the essentially horizontal tubes was studied both theoretically and experimentally;Theoretically, the essentially horizontal tube configuration was found to perform perfectly under conditions of sludge accumulation until the storage depth reached 40% of the tube depth. However, experiments showed that total sludge accumulations of up to 53% tube depth did not cause performance to deteriorate. Accordingly, a maximum allowable storage depth of 40% of the tube diameter is the recommended factor of safety for these horizontal tubes. An inlet and outlet arrangment for the essentially horizontal tubes also was proposed.



Digital Repository @ Iowa State University,

Copyright Owner

Ahmed Ashry Fadel



Proquest ID


File Format


File Size

198 pages