A theory for pressures in cylindrical silos under concentric mixed flow

Abstract

This paper presents a theory for the prediction of pressures in circular silos under concentric mixed flow, assuming an internal flow channel of conical profile with straight but inclined sides. The theory is based on a generalised application of the classical method of 'slice equilibrium' together with additional assumptions based on a treatment of the granular solid as a Coulombic material. Only one of the resulting pair of coupled linear ordinary differential equations may be solved in closed form, while both numerical and approximate closed-form solutions are explored for the other. The derivation of the theory is presented in full and a series of parametric studies explores the predictions and compares these with qualitative observations from experiments. In particular, the significant overpressure that is known to occur at the 'effective transition', where the internal flow channel intersects with the silo wall, may be estimated quantitatively for the first time.

Experimental Pressures Exerted by Maize in Slender Cylindrical Silo: Comparison With Iso 11697

“…As expected, maximum stresses occur during material discharge (Couto et al, 2013a;Jenike et al, 1973b;Sadowski et al, 2020;Sadowski et al, 2011). It is known that for funnel flow as defined in this paper (ISO, 2012), maximum pressures occur despite the discharge flow being less than the mass flow (Jenike et al, 1973b(Jenike et al, , 1973aWójcik et al, 2012).…”

The ‘miniature silo’ test: A simple experimental setup to estimate the effective friction coefficient between the granular solid and a horizontally-corrugated cylindrical metal silo wall

“…This condition may be used to estimate the global average wall friction coefficient by numerical solution based on accurately known Fmax, Wc and an assumption regarding the pressure distribution inside the cylinder to obtain Wg,c. For example, if the classical Janssen assumptions of an axisymmetric vertical pressure state are made [22], represented by a mean vertical pressure pv at any depth z related to the mean horizontal pressure ph by a constant lateral pressure ratio K = ph / pv which in turn is related to the mean frictional shear pt by a constant wall friction coefficient μ, then the expression for Wg,c is:…”

Comment on Maraveas, C. Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods. Appl. Sci. 2020, 10, 3938

“…Some authors [5][6][7][8][9] report pressures versus time at a location along the silo wall. Others report average or maximum pressure at the location along the wall [10][11][12][13]. The methods presented in the international silo design codes are formulated based on maximum pressures measured from experiments at a particular location along the wall of the silo assuming structural properties and discharge rate have no influence on the generated pressure.…”