Threshold pressure experiment of liquid flows through nanochannels and tight cores

Compared with low-permeability oil reservoirs, tight oil reservoirs have more nanopores, complex pore structure, and more obvious nonlinear seepage characteristics. Under the macro-scale channel flow, the influence of micro-forces is often ignored, but micro-forces of the micro-nano-scale have become the main factors affecting the flow. The micro-nano-scale flow is different from the macro-scale flow, and the flow requires the force between the fluid and the micro-nano tubes. The article conducts the threshold pressure experiment of nanochannels and cores, and results show that exists a pressure threshold under liquid flows through nanochannels and cores. The influence of the threshold pressure gradient in the micro-nanochannels is analyzed, and it is found that the nature of the fluid and the diameter of the pores affect the threshold pressure of micro the tube; core experiments prove the threshold pressure gradient exists in the core. The main factors affecting the threshold pressure gradient of the core are the permeability of the core and the nature of the experimental fluid.

A preclinical feasibility study of endoscopic barostat: A possible diagnostic tool for visceral hypersensitivity in functional dyspepsia

Introduction: Diagnosing functional dyspepsia requires excluding organic disease and gastrointestinal function evaluation; however, there are no modalities to evaluate these simultaneously. This preclinical study examined the possibility of an endoscopic barostat. Methods: Ultrathin endoscopy and our newly developed pressure-regulated endoscopic insufflator, which insufflates the gastrointestinal tract until the preset pressure is achieved, were used. The actual intragastric pressure was measured using an optical fiber manometer placed in the stomach. Experiment-1: in an ex vivo experiment, we insufflated the isolated stomach and verified whether the intragastric pressure reached the preset pressure. Experiment-2: we inserted the endoscope orally in a porcine stomach, insufflated the stomach, and verified whether the intragastric pressure reached the preset pressure. Finally, we insufflated the stomach at a random pressure to verify the functional tests for proof-of-concept. Results: Experiment-1: the intragastric pressure reached the preset pressure. After reaching the plateau, the pressure remained stable at the preset pressure (Huber M-value: 1.015, Regression line: 0.988, 95% confidence interval [CI]: 0.994–0.994). Experiment-2: the intragastric pressure reached the preset pressure. After reaching the plateau, the pressure remained stable at the preset pressure (Huber M-value: 1.018, Regression line: 0.971, 95% CI: 0.985–0.986). At randomly preset pressures, the transendoscopic theoretical intragastric pressure detected by the insufflator was correlated with the actual pressure measured by the pressure manometer. Conclusions: This proof-of-concept study shows that a pressure-regulated endoscopic insufflator provides stable intragastric pressure at the preset level, with the potential of an endoscopic barostat to assess visceral the hypersensitivity related to functional dyspepsia.

Influence of Material Parameters on the Contact Pressure Characteristics of a Multi-Disc Clutch

As an essential part of the transmission, the life of the clutch directly affects the stability of the transmission. In this paper, a finite element model and a thermodynamic numerical model of a multi-disc clutch are established to investigate the influence of material parameters on the contact pressure distribution. The pressure distribution index (PDI) is firstly proposed to evaluate the pressure difference among friction pairs. Moreover, the correctness of the numerical model is verified by the clutch static pressure experiment. The results show that increasing the elastic modulus and Poisson’s ratio of the backplate can effectively improve the uniformity of the contact pressure. However, the variations in material parameters of other clutch components can not easily smooth the pressure difference. Therefore, optimized material parameters for the clutch are proposed, where the maximum pressure and temperature differences are reduced by about 27.2% and 10.3%, respectively.

Reciprocating propagation of laser pulse intensity in free space

The constant-speed straight-line propagation in free space is a basic characteristic of light. Recently, several novel spatiotemporal coupling methods, for example, flying focus (or named sliding focus), are developed to control light propagation including velocity and direction. In the method of flying focus, where temporal chirp and longitudinal chromatism are combined to increase the degree of freedom for coherent control, tunable-velocities and even backward-propagation have been demonstrated. Herein, we studied the transverse and longitudinal effects of the flying focus in space and time, respectively, and found in a specific physics interval existing an unusual reciprocating propagation that was quite different from the previous result. By significantly increasing the Rayleigh length in space and the temporal chirp in time, the newly created flying focus can propagate along a longitudinal axis firstly forward, secondly backward, and lastly forward again, and the longitudinal spatial resolution for a clear reciprocation flying focus improves with increasing the temporal chirp. When this new type of light is applied in the radiation pressure experiment, a reciprocating radiation-force can be produced in space-time accordingly. This finding further extends the control of light and might enable important potential applications.

Dynamic simulation of the relationship between pressure and displacement for the waist of elastic pantyhose in the walking process using the finite element method

The inward displacement perpendicular to body surface produced by external pressure is an important index to evaluate pressure comfort and optimal design of tight clothing products. Because of the limited pressure exerted on the human body after wearing compression clothing, the corresponding displacement is generally small, and it is difficult to obtain an accurate displacement value of the human body using general methods. In this paper, we focused on the functional relationship between pressure and displacement when the human body was in the walking state after dressing in elastic pantyhose, and then the displacement data could be easily obtained using this method. Through computerized tomography scanning, establishing of the waist cross-section, finite element simulation, and curve fitting, we finally obtained the functional relationship between the pressure/displacement ratio and angle when the body is dressed in four sample elastic pantyhose during the walking process in this study. In the formula, pressure data can be easily obtained through the pressure experiment, and the corresponding displacement value at any point of the human body can be calculated using the quadratic fitting curve equation. Results indicated that no matter what state the human body was in (static or dynamic) after wearing elastic pantyhose, the relationship between pressure and displacement at the corresponding point remains basically unchanged. That is to say, the relationship between pressure and displacement was basically not affected by the state of the human body when dressed in a tight garment. The conclusions provide an important reference for evaluating pressure comfort and optimizing clothing structure. This method is also applicable to other types of compression clothing.

Experimental Investigation on Flow Field Characteristics of Impinging-Film Cooling

This paper describes an experimental investigation on flow field characteristics of impinging-film cooling. Particle Image Velocimetry (PIV) technology has been applied to observe the effect of blowing ratio ( 0.04 ≤ M ≤ 0.3 ), temperature ratio ( 0.73 ≤ T u ≤ 0.91 ), jet-to-plate pitch ( 1.6 ≤ Z n ≤ 3.2 ), and spacing of impinging holes ( 1.94 ≤ Y n ≤ 3.5 ) on the flow field patterns in an impinging-film cooling test rig under atmospheric pressure. Experiment results show that the near-wall entrained vortex at the downstream of the slit moves downstream of the test rig as the blowing ratio increases, which increases the effective protection length of the film. While the vortex at the end of the inducting slab is stronger, this will increase the mixing in the shear layer. The radial size of the near-wall entrained vortex tends to decrease as the temperature ratio increases at the low blow ratio, and the entrainment effect on the downstream of the slit becomes smaller, causing the separation zone to decrease. Increasing the jet-to-plate pitch, the size of the near-wall entrained vortex increases, and the thickness of the film layer increases, this strengthens the separation effect of the near-wall airflow from the wall surface. The larger the spacing of the impinging holes, the more uneven the velocity distribution of the film.

Rapid Characterisation of Suspensions for Waste Treatment and Resource Recovery

A simple device for the conduct of stepped pressure filtration measurements is described together with methods for making the empirical measurements and interpreting the data obtained. The data interpretation method applies a multi-step systematic approach, with each step supported by statistical justification, to characterise: filter cake particle stress, filtration diffusivity and cake hydraulic resistivity from a single stepped pressure experiment. The methods enable different flocculant materials to be more rapidly and more appropriately screened than conventional jar tests and large scale filtration trials. The methods are applied to the characterisation of a paint residue treated with aluminium sulphate and “PolyClay”.<br>The work shows that the addition of “PolyClay” as a filter aide reduces the hydraulic resistivity at lower solids concentrations but increases it at higher concentrations whilst simultaneously increasing the particle stress. Together these have a combined deleterious effect on the time and energy required to dewater the residues to high solids concentration by filtration. The results also show that a significant change in suspension behaviour occurs between the “PolyClay” doses of 140 mg l^-1 and 660 mg l^-1 and that further changes up to “PolyClay” doses of 1600 mg l^-1 are more modest. The results indicate the existence an opportunity to reduce “PolyClay” dose into a range between 10% and 50% of current practice. In addition the results provide evidence that alternative, centrifuge based, technology is worthy of investigation.

Rapid Characterisation of Suspensions for Waste Treatment and Resource Recovery

A simple device for the conduct of stepped pressure filtration measurements is described together with methods for making the empirical measurements and interpreting the data obtained. The data interpretation method applies a multi-step systematic approach, with each step supported by statistical justification, to characterise: filter cake particle stress, filtration diffusivity and cake hydraulic resistivity from a single stepped pressure experiment. The methods enable different flocculant materials to be more rapidly and more appropriately screened than conventional jar tests and large scale filtration trials. The methods are applied to the characterisation of a paint residue treated with aluminium sulphate and “PolyClay”.<br>The work shows that the addition of “PolyClay” as a filter aide reduces the hydraulic resistivity at lower solids concentrations but increases it at higher concentrations whilst simultaneously increasing the particle stress. Together these have a combined deleterious effect on the time and energy required to dewater the residues to high solids concentration by filtration. The results also show that a significant change in suspension behaviour occurs between the “PolyClay” doses of 140 mg l^-1 and 660 mg l^-1 and that further changes up to “PolyClay” doses of 1600 mg l^-1 are more modest. The results indicate the existence an opportunity to reduce “PolyClay” dose into a range between 10% and 50% of current practice. In addition the results provide evidence that alternative, centrifuge based, technology is worthy of investigation.