Three-dimensional geometry and flow field modeling of forming fabrics

A heightened awareness of the importance of natural convective cooling as a driving factor in design and thermal management of aircraft braking systems has emerged in recent years. As a result, increased attention is being devoted to understanding the buoyancy-driven flow and heat transfer occurring within the complex air passageways formed by the wheel and brake components, including the interaction of the internal and external flow fields. Through application of contemporary computational methods in conjunction with thorough experimentation, robust numerical simulations of these three-dimensional processes have been developed and validated. This has provided insight into the fundamental physical mechanisms underlying the flow and yielded the tools necessary for efficient optimization of the cooling process to improve overall thermal performance. In the present work, a brief overview of aircraft brake thermal considerations and formulation of the convection cooling problem are provided. This is followed by a review of studies of natural convection within closed and open-ended annuli and the closely related investigation of inboard and outboard subdomains of the braking system. Relevant studies of natural convection in open rectangular cavities are also discussed. Both experimental and numerical results obtained to date are addressed, with emphasis given to the characteristics of the flow field and the effects of changes in geometric parameters on flow and heat transfer. Findings of a concurrent numerical and experimental investigation of natural convection within the wheel and brake assembly are presented. These results provide, for the first time, a description of the three-dimensional aircraft braking system cooling flow field.

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Experimental investigation on the three-dimensional flow field from a meltblowing slot die

e-Polymers ◽

10.1515/epoly-2020-0058 ◽

2020 ◽

Vol 20 (1) ◽

pp. 724-732

Author(s):

Changchun Ji ◽

Yudong Wang

Keyword(s):

Flow Field ◽

Three Dimensional ◽

Great Influence ◽

Distribution Characteristics ◽

Air Velocity ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Airflow Distribution ◽

Slot Die ◽

Center Area

AbstractTo investigate the distribution characteristics of the three-dimensional flow field under the slot die, an online measurement of the airflow velocity was performed using a hot wire anemometer. The experimental results show that the air-slot end faces have a great influence on the airflow distribution in its vicinity. Compared with the air velocity in the center area, the velocity below the slot end face is much lower. The distribution characteristics of the three-dimensional flow field under the slot die would cause the fibers at different positions to bear inconsistent air force. The air velocity of the spinning centerline is higher than that around it, which is more conducive to fiber diameter attenuation. The violent fluctuation of the instantaneous velocity of the airflow could easily cause the meltblowing fiber to whip in the area close to the die.

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Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽

10.3390/aerospace8040097 ◽

2021 ◽

Vol 8 (4) ◽

pp. 97

Author(s):

Junfeng Sun ◽

Meihong Liu ◽

Zhen Xu ◽

Taohong Liao ◽

Xiangping Hu ◽

...

Keyword(s):

Flow Field ◽

Film Thickness ◽

Fluid Dynamic ◽

Structural Characteristics ◽

Structural Parameters ◽

Equivalent Stress ◽

Three Dimensional ◽

High Rotational Speed ◽

Flexible Support ◽

Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

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Quantification of Measurement and Model Effects in Monopile Foundation Scour Protection Experiments

Journal of Marine Science and Engineering ◽

10.3390/jmse9060585 ◽

2021 ◽

Vol 9 (6) ◽

pp. 585

Author(s):

Minghao Wu ◽

Leen De Vos ◽

Carlos Emilio Arboleda Chavez ◽

Vasiliki Stratigaki ◽

Maximilian Streicher ◽

...

Keyword(s):

Standard Deviation ◽

Flow Field ◽

Three Dimensional ◽

Small Scale ◽

Maximum Wave Height ◽

Chaotic Flow ◽

The Mean ◽

Scour Protection ◽

Damage Number ◽

Measurement Effects

The present work introduces an analysis of the measurement and model effects that exist in monopile scour protection experiments with repeated small scale tests. The damage erosion is calculated using the three dimensional global damage number S3D and subarea damage number S3D,i. Results show that the standard deviation of the global damage number σ(S3D)=0.257 and is approximately 20% of the mean S3D, and the standard deviation of the subarea damage number σ(S3D,i)=0.42 which can be up to 33% of the mean S3D. The irreproducible maximum wave height, chaotic flow field and non-repeatable armour layer construction are regarded as the main reasons for the occurrence of strong model effects. The measurement effects are limited to σ(S3D)=0.039 and σ(S3D,i)=0.083, which are minor compared to the model effects.

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Transient Three-Dimensional Flow Field Measurements by Means of 3D µPTV in Drying Poly(Vinyl Acetate)-Methanol Thin Films Subject to Short-Scale Marangoni Instabilities

Polymers ◽

10.3390/polym13081223 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1223

Author(s):

Max Tönsmann ◽

Philip Scharfer ◽

Wilhelm Schabel

Keyword(s):

Flow Field ◽

Vinyl Acetate ◽

Three Dimensional ◽

Field Measurements ◽

Initial Assessment ◽

Ambient Conditions ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Short Scale ◽

Dry Film

Convective Marangoni instabilities in drying polymer films may induce surface deformations, which persist in the dry film, deteriorating product performance. While theoretic stability analyses are abundantly available, experimental data are scarce. We report transient three-dimensional flow field measurements in thin poly(vinyl acetate)-methanol films, drying under ambient conditions with several films exhibiting short-scale Marangoni convection cells. An initial assessment of the upper limit of thermal and solutal Marangoni numbers reveals that the solutal effect is likely to be the dominant cause for the observed instabilities.

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