Addressing challenges in reproducibility in radial permeability measurements conforming to the benchmark requirements
Topic(s) : Special Sessions
Co-authors :
Pedro PEDRO MIGUEL SOUSA (BELGIUM), Xiao LIU , Stephan LOMOV (BELGIUM), Jan IVENSAbstract :
Introduction
The accuracy of experimental permeability measurements improved with the recommendations and guidelines from two international benchmarks [1][2] which led to the standardization of these measurements [3]. However, systematic errors in the measurement of the cavity gap, fluid viscosity or optical errors in the visual tracking of a flow front still compromise the comparability of measurements obtained by different rigs. Therefore, these error sources must be identified and minimized to prevent systematic deviations from the expected results.
Methodology
Permeability measurements were conducted in a radial permeameter constituted by a round aluminum upper plate, 250 mm in diameter, and a square glass lower plate (Herasil 102), with dimensions 300x300 mm. Both plates are 30 mm thick. The flow front was recorded by a digital camera through the glass plate. The rig´s installation in a Universal Testing Machine (UTM) enables precise adjustment of cavity thickness while maintaining a constant displacement rate. The distance between plates is measured by laser sensors and the compaction process is automatically stopped when the target thickness is detected. Permeability measurements were conducted with the fabric reinforcements used in the radial benchmark exercise for results comparison accordingly to the proposed methodology [1]. Prior to the measurements, the fluid viscosity was determined as function of temperature, and the cavity thickness was checked with plasticine blocks as suggested in [1]. The measured permeability values were compared to those reported in the radial benchmark exercise. Reported permeability values that did not comply with the cavity deflection limit of 2% or differ more than 30% from the estimated average value were excluded.
Main Conclusions
The lack of a specific protocols for the instrumentation and measurement procedure can lead to uncertainty in verification of the requirements. This includes:
•The uncertainty in the measurement of the plasticine blocks thickness and in the measurement of
the fluid´s viscosity.
•The proposed requirements can be further extended with the verification of interferences in the sensors output voltage. The existence of electrical interferences that surpass the admissible noise level has proved to undermine the performance of a sensor independently of its accuracy.
•While measured K2 showed a good agreement with the average estimated from the benchmark results (between 5 and 7%), the K1 direction was 25% and 33% lower than the average for the lowest and highest fiber volume fractions, respectively. The differences in the K1 direction were attributed to an optical distortion and human factor while extracting the data points in the flow front measurement. Automatic image processing code with fitting parameter considering the partial impregnation of the flow front edge will contribute to the consistency of results.
The accuracy of experimental permeability measurements improved with the recommendations and guidelines from two international benchmarks [1][2] which led to the standardization of these measurements [3]. However, systematic errors in the measurement of the cavity gap, fluid viscosity or optical errors in the visual tracking of a flow front still compromise the comparability of measurements obtained by different rigs. Therefore, these error sources must be identified and minimized to prevent systematic deviations from the expected results.
Methodology
Permeability measurements were conducted in a radial permeameter constituted by a round aluminum upper plate, 250 mm in diameter, and a square glass lower plate (Herasil 102), with dimensions 300x300 mm. Both plates are 30 mm thick. The flow front was recorded by a digital camera through the glass plate. The rig´s installation in a Universal Testing Machine (UTM) enables precise adjustment of cavity thickness while maintaining a constant displacement rate. The distance between plates is measured by laser sensors and the compaction process is automatically stopped when the target thickness is detected. Permeability measurements were conducted with the fabric reinforcements used in the radial benchmark exercise for results comparison accordingly to the proposed methodology [1]. Prior to the measurements, the fluid viscosity was determined as function of temperature, and the cavity thickness was checked with plasticine blocks as suggested in [1]. The measured permeability values were compared to those reported in the radial benchmark exercise. Reported permeability values that did not comply with the cavity deflection limit of 2% or differ more than 30% from the estimated average value were excluded.
Main Conclusions
The lack of a specific protocols for the instrumentation and measurement procedure can lead to uncertainty in verification of the requirements. This includes:
•The uncertainty in the measurement of the plasticine blocks thickness and in the measurement of
the fluid´s viscosity.
•The proposed requirements can be further extended with the verification of interferences in the sensors output voltage. The existence of electrical interferences that surpass the admissible noise level has proved to undermine the performance of a sensor independently of its accuracy.
•While measured K2 showed a good agreement with the average estimated from the benchmark results (between 5 and 7%), the K1 direction was 25% and 33% lower than the average for the lowest and highest fiber volume fractions, respectively. The differences in the K1 direction were attributed to an optical distortion and human factor while extracting the data points in the flow front measurement. Automatic image processing code with fitting parameter considering the partial impregnation of the flow front edge will contribute to the consistency of results.