Experimental Study on the Recirculation of Homogeneous and Stratified Fluid Layers in the Advanced Solar Pond

1994 ◽  
Vol 116 (2) ◽  
pp. 74-78 ◽  
Author(s):  
Y. Keren ◽  
H. Rubin ◽  
G. A. Bemporad
Keyword(s):  
Double Diffusion ◽  
Stratified Fluid ◽  
Experimental Investigations ◽  
Laboratory Setup ◽  
Solar Pond ◽  
Fluid Layers ◽  
Data Density ◽  
And Control ◽  
Stable Flow ◽  
Transient And Steady State

The practical possibilities of constructing and operating a stable flow of homogeneous and stratified fluid layers in a solar pond were investigated in this study. A laboratory setup was prepared to carry out the experimental investigations. Transient and steady-state conditions were analyzed. A numerical model was developed to simulate heat, salt, and momentum transfer in the water body. The model was calibrated with the experimental data. Density and temperature measurements along the laboratory setup showed the configuration to be stable in all of the conditions which were analyzed. These experimental results indicated that through a proper multiselective injection and withdrawal procedure it was possible to create and control the double-diffusion stratified fluid layers, which characterizes the advanced solar pond.

Experimental Investigation on the Rubbing Process of Labyrinth Seals Considering the Material Combination

2020 ◽  
Author(s):  
Lisa Hühn ◽  
Oliver Munz ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer
Keyword(s):  
Turbine Blades ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Contact Forces ◽  
Experimental Investigations ◽  
Process Data ◽  
Labyrinth Seals ◽  
Material Combination ◽  
Higher Temperature ◽  
And Control

Abstract Labyrinth seals are used to prevent and control the mass flow rate between rotating components. Due to thermally and mechanically induced expansions during operation and transient flight maneuvers, a contact, the so-called rubbing process, between rotor and stator cannot be excluded. A large amount of rubbing process data concerning numerical and experimental investigations is available in public literature as well as at the Institute of Thermal Turbomachinery (ITS). The investigations were carried out for different operating conditions, material combinations, and component geometries. In combination with the experiments presented in this paper, the effects of the different variables on load due to rubbing are compared, and discussed with the focus lying on the material combination. The influence of the material on the loads can be identified as detailed as never before. For example, the contact forces in the current experiments are higher due to a higher temperature resistance of Young’s modulus. The analysis will also be based on the rubbing of turbine blades. Design guidelines are derived for labyrinth seals with improved properties regarding tolerance of rub events. Based on the knowledge obtained, guidelines for designing reliable labyrinth seals for future engines are discussed.

Design and Development of a Multi-Module Deployable Manipulator

1999 ◽  
Author(s):  
Kenneth Wong ◽  
Vinod J. Modi ◽  
Clarence W. de Silva ◽  
Arun K. Misra
Keyword(s):  
Real Time ◽  
Experimental Investigations ◽  
Computationally Efficient ◽  
Real Time Control ◽  
Design And Development ◽  
Time Control ◽  
Dynamics And Control ◽  
Manipulator Design ◽  
A Chain ◽  
And Control

Abstract This paper presents the design and development of a Multi-module Deployable Manipulator System (MDMS) as well as a dynamical formulation for it. The system is designed for experimental investigations aimed at dynamics and control of this variable geometry manipulator by implementing different control algorithms to regulate its performance. The manipulator operates in a horizontal plane and is unique in that it comprises of four modules, each of which has one revolute joint and one prismatic joint, connected in a chain topology. Each module has a slewing link of approximately 20cm length and is capable of extending by 15cm. The manipulator design involves the selection and sizing of actuators, the design of mounting and connecting components, and the selection of hardware as well as software for real-time control. The dynamical model is formulated using an O(N) algorithm, based on the Lagrangian approach and velocity transformations. The O(N) character is computationally efficient permitting real-time control of the system.

Microcirculatory effects of norepinephrine in patients with septic shock: a microdialysis study

2020 ◽  
Author(s):  
Amira Fatnassi ◽  
Chihebeddine Romdhani ◽  
Widd Kaabi ◽  
Iheb Labbene ◽  
Zied Hajjej ◽  
...  
Keyword(s):  
Septic Shock ◽  
Lactate Concentration ◽  
Inverse Correlation ◽  
Tissue Perfusion ◽  
Control Group ◽  
Adrenergic Drug ◽  
Microdialysis Study ◽  
And Control ◽  
Stable Flow ◽  
Pyruvate Ratio

Abstract Background: The management of septic shock requires the administration of an alpha-adrenergic drug such as norepinephrine, after optimization of the patient’s preload, to maintain adequate mean arterial pressure. Nevertheless, with optimal macrocirculatory parameters, alterations of tissue perfusion can occur. This study aimed to investigate the effect of norepinephrine dosage on microcirculation parameters, studied by microdialysis, in patients with septic shock. Methods: We conducted a retrospective study. We included all patients aged over 16 years in septic shock. We studied three groups (levosimendan, dobutamine, and control group). We administrated norepinephrine before inclusion, at stable flow for more than an hour. We performed hemodynamic monitoring of macrocirculation by echocardiography. We analyzed microcirculation parameters (lactate, pyruvate, and lactate/pyruvate ratio) every six hours during the first three days, by muscle microdialysis (CMA 600, CMA microdialysis AB, Stockholm, Sweden). We studied correlations between microcirculation parameters and norepinephrine doses.Results: We included thirty patients in the study (ten patients in each group). Demographic characteristics and mortality were comparable across the three groups. In total, we analyzed 390 samples of interstitial muscle fluid. We did not find any correlation between norepinephrine doses and the lactate concentration in the muscle, as well as the ratio of lactate/ pyruvate concentration in the muscle (p > 0.05) for all groups. We found a weak inverse correlation between norepinephrine doses and muscle pyruvate levels (p < 0.05) for the dobutamine group and the control group and but not for the levosimendan group.Conclusions: Noradrenaline dose has little effect on microcirculation when administered for hemodynamic optimization, as recommended by the Surviving Sepsis Campaign.

Swift Trust in Ad Hoc Teams: A Cognitive Task Analysis of Intelligence Operators in Multi-Domain Command and Control Contexts

2020 ◽  
Vol 14 (3) ◽  
pp. 218-241
Author(s):  
August Capiola ◽  
Holly C. Baxter ◽  
Marc D. Pfahler ◽  
Christopher S. Calhoun ◽  
Philip Bobko
Keyword(s):  
Task Analysis ◽  
Ad Hoc ◽  
Cognitive Task ◽  
Command And Control ◽  
Cognitive Task Analysis ◽  
Performance Outcomes ◽  
Experimental Investigations ◽  
Structured Interviews ◽  
Swift Trust ◽  
And Control

Trust is important for establishing successful relationships and performance outcomes. In some contexts, however, rich information such as knowledge of and experience with a teammate is not available to inform one’s trust. Yet, parties in these contexts are expected to work together toward common goals for a relatively brief and finite period of time. This research investigated the antecedents to quickly-formed trust (often referred to as swift trust) in fast-paced, time-constrained contexts. We conducted a cognitive task analysis (CTA) based on 11 structured interviews of subject-matter experts (SMEs) in Intelligence (Intel)—a heterogeneous job category comprising distributed and co-located personnel within multi-domain command and control (MDC2) environments. Eight antecedents to swift trust emerged from these interviews (i.e., ability, integrity, benevolence, communication, mission-focus, self-awareness, shared perspectives/experiences, and calm), with further analysis implying that swift trust is a relevant and emergent state in MDC2 that facilitates reliance. These findings offer implications for teams operating in high-risk distributed contexts and should be expanded through basic experimental investigations as well as applied initiatives.

Experimental investigations on characteristics of boundary layer and control of transition on an airfoil by AC-DBD

2018 ◽  
Vol 32 (08) ◽  
pp. 1850108 ◽  
Author(s):  
Xi Geng ◽  
Zhiwei Shi ◽  
Keming Cheng ◽  
Hao Dong ◽  
Qun Zhao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Boundary Layer Transition ◽  
Plasma Actuators ◽  
Experimental Investigations ◽  
Dbd Plasma ◽  
Layer Transition ◽  
Piv Measurement ◽  
Induced Flow ◽  
And Control

Plasma-based flow control is one of the most promising techniques for aerodynamic problems, such as delaying the boundary layer transition. The boundary layer’s characteristics induced by AC-DBD plasma actuators and applied by the actuators to delay the boundary layer transition on airfoil at Ma = 0.3 were experimentally investigated. The PIV measurement was used to study the boundary layer’s characteristics induced by the plasma actuators. The measurement plane, which was parallel to the surface of the actuators and 1 mm above the surface, was involved in the test, including the perpendicular plane. The instantaneous results showed that the induced flow field consisted of many small size unsteady vortices which were eliminated by the time average. The subsequent oil-film interferometry skin friction measurement was conducted on a NASA SC(2)-0712 airfoil at Ma = 0.3. The coefficient of skin friction demonstrates that the plasma actuators successfully delay the boundary layer transition and the efficiency is better at higher driven voltage.

scholarly journals A highly flexible laboratory setup to demonstrate granular flow characteristics

2020 ◽  
Vol 104 (2) ◽  
pp. 1581-1596
Author(s):  
Thomas Heinze
Keyword(s):  
Granular Flow ◽  
Large Scale ◽  
Numerical Models ◽  
Low Cost ◽  
Experimental Investigations ◽  
Small Scale ◽  
Local Pressure ◽  
Slope Length ◽  
Runout Distance ◽  
Laboratory Setup

Abstract Dynamics of snow avalanches or landslides can be described by rapid granular flow. Experimental investigations of granular flow at laboratory scale are often required to analyze flow behaviour and to develop adequate mathematical and numerical models. Most investigations use image-based analysis, and additional sensors such as pressure gauges are not always possible. Testing various scenarios and parameter variations such as different obstacle shapes and positions as well as basal topography and friction usually requires either the construction of a new laboratory setups for each test or a cumbersome reconstruction. In this work, a highly flexible and modular laboratory setup is presented based on LEGO bricks. The flexibility of the model is demonstrated, and possible extensions for future laboratory tests are outlined. The setup is able to reproduce published laboratory experiments addressing current scientific research topics, such as overflow of a rigid reflector, flow on a bumpy surface and against a rigid wall using standard image-based analysis. This makes the setup applicable for quick scenario testing, e.g. for hypothesis testing or for low-cost testing prior to large-scale experiments, and it can contribute to the validation of external results and to benchmarks of numerical models. Small-scale laboratory setups are also very useful for demonstration purposes such as education and public outreach, both crucial in the context of natural hazards. The presented setup enables variation of parameters such as of slope length, channel width, height and shape, inclination, bed friction, obstacle position and shape, as well as density, composition, amount and grain size of flowing mass. Observable quantities are flow type, flow height, flow path and flow velocity, as well as runout distance, size and shape of the deposited material. Additional sensors allow further quantitative assessments, such as local pressure values.

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