Dimensional and Experimental Analysis of High Hydrostatic Pressure Process; Case Study: Application of Dimensionless Numbers in Millet Starch Rheological Test

Most of the relationships governing many physical phenomena cannot be explicitly derived from survival principles and equations such as cohesion, Bernoulli, momentum or, more generally, the Navier-Stokes equation. The most effective way to solve this problem is to use the principles of dimensional analysis to determine the relationships governing the phenomenon. Using dimensional analysis, one can obtain the numbers and non-dimensional parameters that are involved in determining the equations governing a phenomenon. In this study, for the first time, the method of dimensional analysis was used to obtain the non-dimensional numbers governing the hydrostatic high-pressure process, because there are many variables involved in this process, and the best way to find the relationship between them is to use a dimensional analysis tool. In the next step, after identifying the influential variables using Buckingham's theory, the dimensionless numbers governing the high-pressure process are obtained. Then the measured quantities from the high-pressure tests, the frequency response and the stress-strain rate are given in the form of dimensionless numbers, pre-arranged in order, and the test substance behaviour (the millet starch) is examined. As a result, in addition to the relationship between variables and their relative importance, some material behavioural properties are also represented in the form of dimensionless graphs that differ in behaviour from conventional graphs. In the high-pressure test, the test material was subjected to a hydrostatic pressure of 200 to 600 MPa for 10 to 30 min. The results obtained from the high-pressure test showed that the rheological properties of millet starch, including the complex viscosity, can change with increasing pressure and time of application.