Uncertainty of PIV/PTV based pressure, using velocity uncertainty

Pressure reconstruction from velocity measurements using particle image velocimetry (PIV) and particle tracking velocimetry (PTV) has drawn significant attention as it can provide instantaneous pressure fields without altering the flow. Previous studies have found that the accuracy of the calcualted pressure field depends on several factors including the accuarcy of the velocity measurement, the spatiotemporal resolutions, the method for calculating pressure-gradient, the algorithm for pressure-gradient integration, the pressure boundary condition, etc. Therefore, it is critical and challenging to quantify the uncertainty of the reconstructed pressure field. The recent development of the uncertainty quantification algorithms for PIV and PTV allows for the local and instantaneous uncertainty estimation of velocity measurement, which can be used to infer the pressure uncertainty. In this study, we introduce a framework that propagates the standard velocity uncertainty defined as the standard deviation of the velocity error distribution through the pressure reconstruction process to obtain the uncertainty of the pressure field. The uncertainty propagations through the calculation of the pressure-gradient and the pressure-gradient integration were modeled as linear transformations, which can reproduce the effects of the spatiotemporal resolutions, the numerical schemes, the integration algorithms, and the pressure boundary condition on the accuracy of the resulting pressure fields. The proposed uncertainty estimation approach also considers the effect of the spatiotemporal and componentwise correlation of the velocity errors in common PIV/PTV measurements on the pressure uncertainty.

Testing the altitude attribution and vertical resolution of AirCore measurements with a new spiking method

AirCore samplers have been increasingly used to capture vertical profiles of trace gases reaching from the ground up to about 30 km, in order to validate remote sensing instruments and to investigate transport processes in the stratosphere. When deployed to a weather balloon, accurately attributing the trace gas measurements to the sampling altitudes is nontrivial, especially in the stratosphere. In this paper we present the CO-spiking experiment, which can be deployed to any AirCore on any platform in order to evaluate different computational altitude attribution processes and to experimentally derive the vertical resolution of the profile by injecting small volumes of signal gas at predefined GPS altitudes during sampling. We performed two CO-spiking flights with an AirCore from the Goethe University Frankfurt (GUF) deployed to a weather balloon in Traînou, France, in June 2019. The altitude retrieval based on an instantaneous pressure equilibrium assumption slightly overestimates the sampling altitudes, especially at the top of the profiles. For these two flights our altitude attribution is accurate within 250 m below 20 km. Above 20 km the positive bias becomes larger and reaches up to 1.2 km at 27 km altitude. Differences in descent velocities are shown to have a major impact on the altitude attribution bias. We parameterize the time lag between the theoretically attributed altitude and the actual CO-spike release altitude for both flights together and use it to empirically correct our AirCore altitude retrieval. Regarding the corrected profiles, the altitude attribution is accurate within ±120 m throughout the profile. Further investigations are needed in order to test for the scope of validity of this correction parameter regarding different ambient conditions and maximum flight altitudes. We derive the vertical resolution from the CO spikes of both flights and compare it to the modeled vertical resolution. The modeled vertical resolution is too optimistic compared to the experimentally derived resolution throughout the profile, albeit agreeing within 220 m. All our findings derived from the two CO-spiking flights are strictly bound to the GUF AirCore dimensions. The newly introduced CO-spiking experiment can be used to test different combinations of AirCore configurations and platforms in future studies.

Combustion of Low-Concentration Gas in a Porous Media Burner: Reactor Design and Optimization

In order to utilize the low-concentration gas directly discharged into the atmosphere from 1.1% to 1.50% in coal mine production, the heat storage and oxidation equipment of gas was improved, and the heat storage and safety of gas under high-temperature environment were tested. The experimental results show that the regenerative oxidation system could provide a high-temperature oxidation environment of 1000°C for gas oxidation after changing the heating mode and enhancing the sealing property. The pressure curves of air and gas in the burner were similar. With the increase of gas concentration, the pressure difference between inlet and outlet tended to increase linearly with a minimum pressure differential of 4 kPa (air) and a maximum pressure differential of 11 kPa (1.50% gas). The internal pressure was relatively stable without an instantaneous pressure surge or explosion. The result of this study provides a reference for further research on the low-concentration gas regeneration oxidation unit at high temperatures.

RESEARCH OF THE IMPACT ON PRODUCTIVITY OF PARAMETERS AND OPERATING MODES OF THE VIBRATION MACHINE DRIVE FOR CLEANING AND WASHING CONTAMINATIONS BY SUBMERGTD STREAM JET WITH SOLID PARTICLES

Analyzed the methods of cleaning and washing, the design of machines with a vibration drive. The choice of a specific method of cleaning and washing is determined depending on the type and properties of contaminants, on the requirements for the cleanliness of products, and the type of production. The scheme of operation of a vibrating machine for cleaning and washing machine parts in a pulsating flow of liquid with solid particles is considered and parameters that affect its performance are determined. The results of studies of physical phenomena during the formation of a pulsating submerged jet are presented, and the influence of design parameters and modes of the drive robots on the maximum jet pressure is determined. An analytical dependence of the maximum instantaneous pressure of the jet has been obtained experimentally, which makes it possible to determine the optimal ratios of parameters when designing a vibration machine for cleaning and washing contaminants.

Effect of the compressible spaces on the performance of piezoelectric pump with rhombic micro-displacement amplifying vibrator

This paper proposes a rhombic micro-displacement amplifying vibrator piezoelectric pump which introduces a mechanism called “compressible space” near inlet and outlet valves. The working principle of compressible space is presented and a simulation is conducted to verify the effect. Analysis reveals that the compressible space can reduce the transmission time of the pressure wave thus increasing the efficiency of the valves, and suppress the pressure fluctuation due to the rapid closing of the valves. The simulation shows that the pressure fluctuation in the pipe is relieved and the instantaneous pressure wave can be mostly absorbed with the presence of compressible space. Then the effect of three sizes of compressible space (area approximately 100, 150, 200 mm2), the number of compressible space (two and a single), the distance between the compressible space and the valve (near the valve and in the middle of the pipe) on the pump performance is experimentally investigated. Experimental results demonstrate that the effect of two compressible spaces is better than only one, and medium-sized compressible spaces have the best comprehensive effect. Meanwhile, when the compressible spaces are near the valves, the effect is better.

Testing the altitude attribution and vertical resolution of AirCore measurements with a new spiking method

AirCores have been increasingly used to capture vertical profiles of trace gases reaching from the ground up to about 30 km, in order to validate remote sensing instruments and to investigate transport processes in the stratosphere. When deployed to a weather balloon, accurately attributing the trace gas measurements to the sampling altitudes is non-trivial especially in the stratosphere. In this paper we present the CO-spiking experiment, which can be deployed to any AirCore on any platform in order to evaluate different computational altitude attribution processes and to experimentally derive the vertical resolution of the profile by injecting small volumes of signal gas at predefined GPS-altitudes during sampling. We performed two CO-spiking flights with an AirCore from the Goethe-University of Frankfurt (GUF) deployed to a weather balloon in Traînou, France in June 2019. The altitude retrieval based on an instantaneous pressure equilibrium assumption slightly overestimates the sampling altitudes, especially at the top of the profiles. For these two flights our altitude attribution is accurate within 250 m below 20 km. Above 20 km the bias becomes larger and reaches up to 1.2 km at 27 km altitude. Differences in descent velocities are uncovered to have a major impact on the altitude attribution bias. We identified the time lag between the theoretically attributed altitude and the actual CO-spike release altitude to be a possible empirical correction parameter for our AirCore altitude retrieval across different flights. Regarding the corrected profiles, the altitude attribution is accurate within 120 m throughout the profile. Further investigations are needed in order to test for the scope of validity of this correction parameter regarding different ambient conditions and maximum flight altitudes. We derive the vertical resolution from the CO-spikes of both flights and compare it to the modelled vertical resolution. The modelled vertical resolution is better than the experimentally derived resolution throughout the profile, albeit agrees within 220 m. All our findings derived from the two CO-spiking flights are strictly bound to the GUF AirCore dimensions. The newly introduced CO-spiking experiment can be used to test different combinations of AirCore configurations and platforms in future studies.

Kinetics Of Fruit Crops Drying With Instant Pressure Release

The article covers results of research of drying process of apricot fruits by the method of three-stage energy supply. The main stages of drying have been defined, including: pulsed infrared heating, instantaneous pressure impact, convective drying. Optimal technological parameters of energy supply in the process of drying apricot fruits at each stage have been developed. The choice of the method for the experimental determination of the drying speed by the parameters of the drying agent for the capillary-porous material is substantiated. The sequence of changes in moisture content in a given material under the influence of a three-stage energy supply is described. The conditions for drying fruits are established and the values of the drying speed in the first period for various methods of energy supply have been selected.