COBEM99

S8 Engenharia Aeroespacial

Title:

VISUALIZAÇÃO DE FLUIDOS EM ALTA VELOCIDADE POR PROCESSAMENTO DE CAMPOS INTERCALADOS DE IMAGEM USANDO A TÉCNICA "PIV"

Summary :

ABSTRACT MEASURING HIGH VELOCITY IN FLUID FLOWS IS NOT AN EASY TASK. PROCESSING IMAGE TECHNIQUES, SUCH AS PARTICLE IMAGE VELOCIMETRY (PIV), WITH CONTINUOUS LASER SHEET AND CONVENTIONAL CCD CAMERAS, OPERATING AT 30 FRAMES PER SECOND, ALLOWS GOOD MEASUREMENT, ONLY FOR SLOW FLOWS. FOR A FASTER FLOW, THIS TECHNIQUE, UNFORTUNATELY, IS NOT SUITABLE. BUT AT PRESENT TIME, A NEW GENERATION OF DIGITAL CCD-DV CAMERAS, WITH CONTROLLED SHUTTER VELOCITY, IS BEEN INTRODUCED IN THE MARKED. THIS NEW FEATURE TURNED POSSIBLE MEASURE VELOCITIES UP TO 100 M/S, EVEN WITHOUT PULSATING THE LASER LIGHT. THIS WORK SHOWS A TECHNIQUE FOR PROCESSING FRAMES CAPTURED AT DIFFERENT SHUTTER VELOCITY AND RECORDED INTO A DIGITAL DVT (DIGITAL VIDEOTAPE). ONE IMAGE OF DOUBLE FIELD (EVEN AND ODD FIELDS) IS CAPTURED AND THE PROCESSING IS DONE BETWEEN BOTH FIELDS. AN IMAGE, CAPTURED WITH VARIABLE SHUTTER VELOCITY (RANGING FROM 1/30 UP TO 1/10000 SECONDS), IS RECORDED ONTO A DVT TO BE, DIGITIZED BY AN INTERFACE BOARD INTO A MICROCOMPUTER AND PROCESSED, AFTERWARDS. THE PROCESSING ALGORITHM IS BASED ON A CROSS CORRELATION AND AUTOCORRELATION TECHNIQUE BETWEEN BOTH FIELDS AND A POST-PROCESSING PROCEDURE PRESENTS THE FLOW FIELD RESULTS. KEY-WORDS: FLOW VISUALIZATION, PARTICLE IMAGE VELOCIMETRY

Author :

Ferreira, Vilson Carlos da Silva
Van Der Laan, Flávio Tadeu

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