Simulation on using Cross-Correlation Technique for Two-Phase Liquid/Gas Flow Measurement for Ultrasonic Transmission Tomography N. M. Nor Ayob 1 , S. Yaacob 1 , Z. Zakaria 1 , M. H. Fazalul Rahiman 2 , R. Abdul Rahim 3 1 Tomography Imaging Research Group, School of Mechatronic Engineering, Universiti Malaysia Perlis, 02600 Arau, Perlis, Malaysia. 2 hafiz@unimap.edu.my 1 normuzakkir@mail.com 3 Process Tomography Research Group (PROTOM), Control and Instrumentation Engineering Department, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia. 3 ruzairi@fke.utm.my Abstract— Combining Ultrasonic Transmission Tomography (UTT) with the cross-correlation flow measurement technique can provide more information on the flow than usual. A simulated dual-plane UTT system for use on laboratory and plant-scale process equipment has been developed on the basis of this idea. This paper focuses on the correlator used to cross- correlate the tomogram images between the downstream and upstream plane of the simulated dual-plane ultrasonic transmission tomography system. This paper proposed the use of 2D correlation coefficient for the correlator and the result of its use is discussed. The principle of measurement of the local gas velocity distribution in a bubbly gas/liquid pipe flow which is based on cross-correlation of two plane images is also described. Initial experimental results illustrate the feasibility of the method presented here. Keywords— Cross-correlation, Frozen Pattern, Correlation Coefficient, Dual-Plane Simulation, Ultrasonic Transmission Tomography. I. INTRODUCTION A new generation of process-parameter-measurement techniques, process tomography (PT), has been developing rapidly in recent years and now has come to the stage of industrial applications. PT techniques provide novel means of visualizing the internal behaviour of an industrial process, such as gas/liquid two-component flows in oil pipelines and processes of mixing or separation in plant vessels. Numerous valuable information for measurement, online monitoring and control of industrial processes can be administered using Process Tomography systems than can most traditional equipment [1] – [3]. Many suitable applications of UTT (Ultrasonic Transmission Tomography) have been found in monitoring of industrial processes and environmental areas, such as monitoring of the measurements of gas–liquid mixing in a stirred vessel [4]–[6], detection of leakages from buried pipes [7] and industrial monitoring of hydro cyclone operation [8]. UT has been proven as one of the important tools that can be utilised to improvise the operation efficiency of such applications as this results in accurate measurement and control of hydrodynamic parameters such as flow regime and flow rate [9],[10]. The non-invasive nature of the UTT sensing method also has helped in attracting great interest from researches and engineers in various fields [11]. Like other PT systems, a typical UTT system is composed of four parts, as shown in Fig. 1: (1) the sensor, (2) the data acquisition system (DAS), (3) the image reconstruction and (4) the computer. There has been an increasing use of instrumentation in the process and energy conversion industries for many purposes including safety, energy saving, product quality, operational efficiency and manpower saving. More recently the advent of process computer systems, which have enhanced these functions particularly in the fields of complex control and management information, has increased the requirement for the measurement of plant parameters. Flow measurement is a particularly important aspect of plant instrumentation. Cross correlation technique are ideally suited to the measurement of multi-phase flows while providing more information on the flow than traditional measurement instrumentation. It was proven that cross correlation technique is technically highly successful, although it was not adopted for process use because of prohibitively high cost of on-line electronic correlators at the time (the late 1950s) [12]. Signal Conditioning (1) (2) (3) (4) (1) Fig. 1 Block Diagram of Ultrasonic Transmission Tomography 2010 6th International Colloquium on Signal Processing & Its Applications (CSPA) 322 978-1-4244-7122-5/10/$26.00 ©2010 IEEE