Evaluation of pressures in slender cylindrical silos: experimental and numerical study

Abstract

The main objective of this work is to understand the actions, mainly the pressures on the walls, in slender silos. For this, slender cylindrical silos were studied experimentally and by numerical simulation. This thesis allowed the experimental validation of a slender silo model. Based on this model, analyzes were performed with different configurations to understand the static and dynamic pressures in slender silos. Thus, the articles, “Static and dynamic pressure measurements of maize grain in silos under different conditions”, published in the scientific journal Biosystems Engineering 209 (2021) 180-199, “Evaluation of pressures in slender silos varying hopper angle and silo slenderness”, published in the scientific journal Powder Technology 394 (2021) 478- 495, “Experimental pressures exerted by maize in slender cylindrical silo: comparison with ISO 11697”, published in the scientific journal Engenharia Agrícola 41 (2021) 576-590 correspond to the validation of the composite station by a pilot silo, a bucket elevator and a storage silo. The first article describes the complete instrumentation of the pilot silo, the subsequent calibration with water and the final validation using maize as a stored product. In addition, interesting findings were found due to the slenderness of the silo. The second article, continuing the first results of the investigation, evaluated the variables hopper angle and slender (height / diameter ratio). In this article, static and dynamic pressures were evaluated at all stages of the test. In addition, the types of flow were also evaluated, presenting unprecedented results. The third, continuing the experimental studies “Effect of the hopper angle of a silo on the vertical stress at the cylinder-to-hopper transition”, published in the scientific journal Agronomy 12 (2022) 830-844, presents static and dynamic results of the vertical force in the silo/hopper transition, analyzing the different flows and different hopper angles using h/d = 3.6 ratio. The fourth article, continuing the first results of the investigation, evaluated the angle of the hopper. In this article, static and dynamic pressures were evaluated and compared with the ISO standard. The fifth article, “Influence of specific weight and wall friction coefficient on normal pressures in silos using the Finite Element Method”, published in the scientific journal Engenharia na Agricultura-REVENG 29 (2021) 192- 203 evaluates numerical simulation in silos, using finite elements models to evaluate the normal pressures on the wall with different simulations of specific weights and coefficient of friction with the wall, since these two variables have a direct influence on the silo flows and pressures. This article deals with an initial model, presenting the first validations of these parameters in slender cylindrical silos. The sixth, “The influence of flow pattern and hopper angle on static and dynamic pressures in slender silos”, in process to be submitted to Powder Technology journal, presents static and dynamic results of horizontal and friction pressures, K coefficient, analyzes the maximum pressures, comparing with Eurocode 1, part 4, analyzing the types of flows and five different angles of hoppers using h/d 3.6 ratio. The installation used for the experimental tests is based on the model by Pieper and Schütz (1980), providing the basis for the DIN 1055-6 standard (DIN, 2005). The experimental station is modular and proved to be versatile, allowing numerous configuration possibilities due to its instrumentation and structural independence.