“…According Ergun equation, the relationship between pressure differential (Δp=pin−pout) and fabric air permeability in compressible flow is:where a , b are the viscous air permeability coefficient and inertial air permeability coefficient of the fabric in incompressible flow, respectively. which can be expressed as:where μ is dynamic viscosity of air, ε is the fabric porosity, According to, 21 the fabric characteristic length D could be as the function of fabric length and fabric porosity (D=6L(1−ε)), then the viscous air permeability coefficient and inertial air permeability coefficient of the fabric can be obtained:Figure 1.Fabric structure under pressure differential.…”
Section: Mathematical Modelmentioning
confidence: 99%
“…where μ is dynamic viscosity of air, ε is the fabric porosity, According to, 21 the fabric characteristic length D could be as the function of fabric length and fabric porosity (D ¼ 6Lð1 À εÞ), then the viscous air permeability coefficient and inertial air permeability coefficient of the fabric can be obtained:…”
In order to investigate the dynamics and vortex shedding of flexible supersonic canopies, a compressible permeability model combined with fabric structure parameters is proposed, and the periodic oscillation of the supersonic parachute which is referred to as breathing phenomenon is simulated based on the Arbitrary Langrangian Eulerian (ALE) method. The calculated results by new permeability model are consistent with the experimental results. The underlying mechanism of canopy breathing motion is then investigated. Moreover, the influence of canopy permeability on breathing phenomenon of supersonic parachute is analyzed. The results indicate that the periodic growth and shedding of the canopy vortex causes the variation of the pressure differential, which finally lead to the periodic oscillation of the canopy. With the increase of fabric permeability, the vortex rolled up from the canopy skirt move backward and become more slender. The influence of vortex shedding on canopy breathing motion weakened. Those lead to the decrease of the average value of canopy projected area and parachute dynamic load. So are the oscillation amplitude and frequency. The parachute deceleration performance decreases while the parachute swing angle decreases as the canopy permeability increases.
“…According Ergun equation, the relationship between pressure differential (Δp=pin−pout) and fabric air permeability in compressible flow is:where a , b are the viscous air permeability coefficient and inertial air permeability coefficient of the fabric in incompressible flow, respectively. which can be expressed as:where μ is dynamic viscosity of air, ε is the fabric porosity, According to, 21 the fabric characteristic length D could be as the function of fabric length and fabric porosity (D=6L(1−ε)), then the viscous air permeability coefficient and inertial air permeability coefficient of the fabric can be obtained:Figure 1.Fabric structure under pressure differential.…”
Section: Mathematical Modelmentioning
confidence: 99%
“…where μ is dynamic viscosity of air, ε is the fabric porosity, According to, 21 the fabric characteristic length D could be as the function of fabric length and fabric porosity (D ¼ 6Lð1 À εÞ), then the viscous air permeability coefficient and inertial air permeability coefficient of the fabric can be obtained:…”
In order to investigate the dynamics and vortex shedding of flexible supersonic canopies, a compressible permeability model combined with fabric structure parameters is proposed, and the periodic oscillation of the supersonic parachute which is referred to as breathing phenomenon is simulated based on the Arbitrary Langrangian Eulerian (ALE) method. The calculated results by new permeability model are consistent with the experimental results. The underlying mechanism of canopy breathing motion is then investigated. Moreover, the influence of canopy permeability on breathing phenomenon of supersonic parachute is analyzed. The results indicate that the periodic growth and shedding of the canopy vortex causes the variation of the pressure differential, which finally lead to the periodic oscillation of the canopy. With the increase of fabric permeability, the vortex rolled up from the canopy skirt move backward and become more slender. The influence of vortex shedding on canopy breathing motion weakened. Those lead to the decrease of the average value of canopy projected area and parachute dynamic load. So are the oscillation amplitude and frequency. The parachute deceleration performance decreases while the parachute swing angle decreases as the canopy permeability increases.
“…In the face of the problems above, textile companies are seeking to quantify the properties of wool fabrics in order to establish a mathematical link between the processing process and the finished style, and to further realize the automated design of the processing process. Based on the theory that the microstructure of a fabric determines its macroscopic properties [4][5][6][7][8][9], it is feasible to introduce the microstructure instead of traditional quality control methods in the selection of raw materials, the design process and the production processes of fabric processing [10]. There are three main geometrically described parameters (shown in Figure 1) that characterize the microstructure: the yarn's properties (e.g., yarn diameter R), the yarn's spacing D and the topology, expressed in terms of the path of the center points [11].…”
The trends of “fashionalization”, “personalization” and “customization” of wool fabrics have prompted the textile industry to change the original processing design based on the experience of engineers and trial production. In order to adapt to the promotion of intelligent production, the microstructure of wool fabrics is introduced into the finishing process. This article presents an automated method to extract the microstructure from the micro-CT data of woven wool fabrics. Firstly, image processing was performed on the 3D micro-CT images of the fabric. The raw grayscale data were converted into eigenvectors of the structure tensor to segment the individual yarns. These data were then used to calculate the three parameters of diameter, spacing and the path of the center points of the yarn for the microstructure. The experimental results showed that the proposed method was quite accurate and robust on woven single-ply tweed fabrics.
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