Total Pressure Correction of a Sub-Miniature Five-Hole Probe in Areas of Pressure Gradients

2012 ◽  
Author(s):  
J. Town ◽  
A. Akturk ◽  
C. Camcı
Keyword(s):  
Pressure Measurement ◽  
Measurement Errors ◽  
Total Pressure ◽  
Pressure Gradients ◽  
Pressure Data ◽  
Flow Conditions ◽  
Complex Flow ◽  
Ducted Fan ◽  
The Difference ◽  
Best Fit

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances.

Design methodology of a highly loaded tandem rotor and its performance analysis under clean and distorted inflows

2021 ◽  
pp. 095440622110160
Author(s):  
Amit Kumar ◽  
AM Pradeep
Keyword(s):  
Experimental Analysis ◽  
Total Pressure ◽  
Pressure Rise ◽  
Pressure Gradients ◽  
Complex Flow ◽  
Angle Variation ◽  
Stall Margin ◽  
Rotor Design ◽  
Flow Through ◽  
Aerodynamic Parameters

Compact and efficient compressor design is one of the key challenges in aero-engine development. The flow through a compressor is exposed to adverse pressure gradients, which limits the maximum allowable flow turning in a compressor blade. Tandem blading is an interesting concept to achieve a higher total pressure rise by augmenting the flow turning angle. Variation in axial overlap and percentage pitch of the forward and aft blade elements largely influences the behavior of the tandem configuration. In the present study, the genetic algorithm is used to optimize the axial overlap and the percentage pitch for the tandem rotor. Results indicate that a lower axial overlap and higher percentage pitch results in optimum performance. The paper presents the parametric study of four tandem configurations with different axial overlaps and percentage pitches. A detailed experimental analysis of the four different tandem configurations is included in this paper. The behavior of the tandem rotor is examined under the clean and radially distorted inflow. Further, a comparison is drawn with a conventional single rotor in terms of aerodynamic parameters such as total pressure rise, axial velocity, and stall margin. The experimental analysis is supplemented by some interesting computational results, which are included to provide some insight into the complex flow field of the tandem rotor. Tandem rotor design is observed to have a higher sensitivity to radial tip inflow distortion. The upstream shift of the aft rotor blade adversely affects the total pressure rise and stall margin of the tandem rotor.

Accuracy of the Phoenix and Viking atmospheric pressure measurements: impact on detecting the climate change on Mars

2021 ◽  
Author(s):  
Henrik Kahanpää ◽  
Jouni Polkko ◽  
Michael Daly
Keyword(s):  
Climate Change ◽  
Pressure Measurement ◽  
Atmospheric Pressure ◽  
Barometric Pressure ◽  
Pressure Measurements ◽  
Pressure Data ◽  
Phoenix Mission ◽  
The Difference ◽  
The Phoenix

<p>Attempts have been made to detect secular changes in the Martian climate by comparing surface atmospheric pressure measurements separated by several decades [1][2]. Such multi-mission studies require information on the exact accuracies of the corresponding pressure measurements. In this presentation, we discuss results of our recently published study on the quality of the pressure data measured by the Mars Phoenix lander [3]. In addition, we evaluate the absolute accuracy of the Viking pressure data by using (less well known) sources in the literature [4][5].</p> <p>Our results show that at the beginning of the Phoenix mission the offset of the pressure measurement was between -4.8 Pa and +0.1 Pa. The drift of the sensor during the mission was between -0.5 Pa and +3.4 Pa. Thus, the Phoenix pressure measurement was much more accurate than was reported immediately after the mission [6]. However, the systematic error of the Viking pressure data could be up to 8.8 Pa.</p> <p>Haberle and Kahre (2010) found the Phoenix surface pressures to be ~10 Pa higher than the Viking surface pressures after correcting for elevation differences and dynamics [1]. Although our results show the Phoenix measurement to be more accurate than assumed by Haberle and Kahre (2010), the difference they found could still be explained by the uncertainty of the Viking pressure data. On the other hand, our results show that the Phoenix pressure data can be used as an accurate comparison point for future surface pressure measurements on Mars.</p> <p><strong>References:</strong></p> <p>[1] Haberle and Kahre, "Detecting secular climate change on Mars ", <em>Mars</em>, 5, 68–75, 2010.</p> <p>[2] Batterson et al., "Secular Climate Change on Mars: An Update", <em>AGU Fall Meeting</em>, 2017.</p> <p>[3] Kahanpää et al., "The quality of the Mars Phoenix pressure data", <em>Planet. Space Sci.</em>, 181, 104814, 2020.</p> <p>[4] Seiff, "The Viking atmosphere structure experiment - Techniques, instruments, and expected accuracies", <em>Space Sci. Instrum.</em>, 2, 381–423, 1976.</p> <p>[5] Mitchell, "Evaluation of Viking Lander barometric pressure sensor", <em>NASA</em> <em>Technical Memorandum</em>, NASA-TM-X-74020, 1977.</p> <p>[6] Taylor et al., "On pressure measurement and seasonal pressure variations during the Phoenix mission", <em>J. Geophys. Res.</em>, 115, E00E15, 2010.</p> <p><strong>Acknowledgments:</strong></p> <p>The contribution of H. Kahanpää in this study was supported by The Finnish Cultural Foundation [grant number 00170395]. The contribution of M. Daly was supported by the Canadian Space Agency. We wish to thank Germán Martínez (USRA/LPI) for providing a copy of reference article [4].</p>

scholarly journals THE VALUE OF ROBUST STATISTICAL FORECASTS IN THE COVID-19 PANDEMIC

2021 ◽  
Vol 256 ◽  
pp. 19-43
Author(s):  
Jennifer L. Castle ◽  
Jurgen A. Doornik ◽  
David F. Hendry
Keyword(s):  
Structural Change ◽  
Measurement Errors ◽  
Epidemiological Models ◽  
Short Term ◽  
Data Measurement ◽  
Policy Interventions ◽  
Changing Trends ◽  
Technological Advances ◽  
The Difference ◽  
The Uk

The Covid-19 pandemic has put forecasting under the spotlight, pitting epidemiological models against extrapolative time-series devices. We have been producing real-time short-term forecasts of confirmed cases and deaths using robust statistical models since 20 March 2020. The forecasts are adaptive to abrupt structural change, a major feature of the pandemic data due to data measurement errors, definitional and testing changes, policy interventions, technological advances and rapidly changing trends. The pandemic has also led to abrupt structural change in macroeconomic outcomes. Using the same methods, we forecast aggregate UK unemployment over the pandemic. The forecasts rapidly adapt to the employment policies implemented when the UK entered the first lockdown. The difference between our statistical and theory based forecasts provides a measure of the effect of furlough policies on stabilising unemployment, establishing useful scenarios had furlough policies not been implemented.

Abstract 15322: Trifecta vs. Mitroflow: Superior Hemodynamics Despite Similar Design

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Mahmoud Diab ◽  
Gloria Faerber ◽  
Ivliane Tsanava ◽  
Martin Breuer ◽  
Mario Walther ◽  
...  
Keyword(s):  
Aortic Annulus ◽  
Special Consideration ◽  
Pressure Gradients ◽  
Valve Design ◽  
Innovative Design ◽  
Mean Pressure ◽  
The Difference ◽  
Different Diameters

Purpose: Hemodynamic results of stented tissue valves are influenced by both valve design and sizing strategy. The Mitroflow and the Trifecta have an innovative design where the pericardium is wrapped around the stent. The goal of this study was to compare both valves giving special consideration to the suggested sizing strategies. Methods: We obtained pressure gradients from discharge echocardiograms from all patients having received an isolated Trifecta (n=104) or Mitroflow (n=246) between 01/2007 and 01/2014. We compared the results by size label and by the most likely selected size according to the suggested sizing strategy. This is important because the prostheses, despite having a similar design, have different diameters for the same size label and different sizing strategies. Results: The majority of implanted valves were size labels 21 and 23 (82.7% of the Trifecta and 74.8% of the Mitroflow). Mean pressure radients were lowest with Trifecta (Trifecta vs. Mitroflow, label-21: 11.4±4.65 vs 13.6±5.23 mmHg, label-23: 9.23±3.38 vs. 11.8±4.42 mmHg, p< 0.05, and label-25: 11.2±4.97 vs 12.0±4.46 mmHg, n.s.). The sizers for the Trifecta are metric, while those for the Mitroflow are 2-3 mm larger than the corresponding size label. It is therefore likely that for a patient with a 23 mm aortic annulus, a 23 Trifecta but often only a 21 Mitroflow is selected. Thus, comparing the Trifecta to the Mitroflow not by size label but by selected valve (e.g., 23 vs. 21) would therefore only increase the difference. Conclusion: The Trifecta shows a hemodynamic advantage over the Mitroflow which is not likely associated with the applied sizing strategy.

scholarly journals Comparison of anterior retraction and anchorage control between en masse retraction and two-step retraction: A randomized prospective clinical trial

2018 ◽  
Vol 89 (2) ◽  
pp. 190-199 ◽  
Author(s):  
Patricia Pigato Schneider ◽  
Luiz Gonzaga Gandini Júnior ◽  
André da Costa Monini ◽  
Ary dos Santos Pinto ◽  
Ki Beom Kim
Keyword(s):  
Clinical Trial ◽  
Treatment Group ◽  
Secondary Outcome ◽  
Space Closure ◽  
The Difference ◽  
Maxilla And Mandible ◽  
Anchorage Loss ◽  
Bimaxillary Protrusion ◽  
Best Fit ◽  
En Masse Retraction

ABSTRACT Objectives: The purpose of this two-arm parallel trial was to compare en masse (ER) and two-step retraction (TSR) during space closure. Materials and Methods: Forty-eight adult patients with bimaxillary protrusion who were planned for treatment with extraction of four first premolars were enrolled. All patients were randomly allocated in a 1:1 ratio to either the ER (n = 24) group or the TSR (n = 24) group. The main outcome was the amount of posterior anchorage loss in the molars and the retraction of the incisors between ER and TSR; the difference in incisor and molar inclination was a secondary outcome. Lateral cephalometric radiographs and oblique cephalometric radiographs at 45° were taken before retraction (T1) and after space closure (T2). Cephalograms were digitized and superimposed on the anatomic best fit of the maxilla and mandible by one operator who was blinded to the treatment group. Results: Neither incisor nor molar crown movements showed any significant differences between the ER and TSR. There were no significant differences in the tipping of incisors and molars between the two groups. Conclusions: No significant differences existed in the amount of retraction of incisors and anchorage loss of molars between ER and TSR. Changes in incisor and molar tipping were similar, with the crowns showing more movement than the apex.

scholarly journals Determination of Vapor-Liquid Equilibrium from Total Pressure Measurement

1971 ◽  
Vol 14 (4) ◽  
pp. 252-256 ◽  
Author(s):  
Kunio Nagahama ◽  
Seijiro Suda ◽  
Toshikatsu Hakuta ◽  
Mitsuho Hirata
Keyword(s):  
Pressure Measurement ◽  
Total Pressure ◽  
Liquid Equilibrium ◽  
Vapor Liquid Equilibrium ◽  
Vapor Liquid

Predicting Turbulent Boundary Layer Wall Pressure Fluctuations in Adverse Pressure Gradients

2005 ◽  
Author(s):  
Frank J. Aldrich
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Pressure Fluctuations ◽  
Adverse Pressure Gradient ◽  
Wall Pressure ◽  
Prediction Tool ◽  
Pressure Gradients ◽  
Wall Pressure Fluctuations ◽  
The Difference

A physics-based approach is employed and a new prediction tool is developed to predict the wavevector-frequency spectrum of the turbulent boundary layer wall pressure fluctuations for subsonic airfoils under the influence of adverse pressure gradients. The prediction tool uses an explicit relationship developed by D. M. Chase, which is based on a fit to zero pressure gradient data. The tool takes into account the boundary layer edge velocity distribution and geometry of the airfoil, including the blade chord and thickness. Comparison to experimental adverse pressure gradient data shows a need for an update to the modeling constants of the Chase model. To optimize the correlation between the predicted turbulent boundary layer wall pressure spectrum and the experimental data, an optimization code (iSIGHT) is employed. This optimization module is used to minimize the absolute value of the difference (in dB) between the predicted values and those measured across the analysis frequency range. An optimized set of modeling constants is derived that provides reasonable agreement with the measurements.

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