scholarly journals Simultaneous Optimal Estimation of Roughness and Minor Loss Coefficients in a Pipeline

2020 ◽  
Vol 25 (3) ◽  
pp. 56 ◽  
Author(s):  
Ildeberto Santos-Ruiz ◽  
Francisco-Ronay López-Estrada ◽  
Vicenç Puig ◽  
Guillermo Valencia-Palomo
Keyword(s):  
Steady State ◽  
Nonlinear Optimization ◽  
Optimal Estimation ◽  
Head Loss ◽  
Pressure Measurements ◽  
Loss Coefficients ◽  
Fitting Error

This paper presents a proposal to estimate simultaneously, through nonlinear optimization, the roughness and head loss coefficients in a non-straight pipeline. With the proposed technique, the calculation of friction is optimized by minimizing the fitting error in the Colebrook–White equation for an operating interval of the pipeline from the flow and pressure measurements at the pipe ends. The proposed method has been implemented in MATLAB and validated in a serpentine-shaped experimental pipeline by contrasting the theoretical friction for the estimated coefficients obtained from the Darcy–Weisbach equation for a set of steady-state measurements.

Internal Flow Losses: A Fresh Look at Old Concepts

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Bastian Schmandt ◽  
Heinz Herwig
Keyword(s):  
Flow Field ◽  
Entropy Generation ◽  
Mechanical Energy ◽  
Internal Flow ◽  
Second Law Of Thermodynamics ◽  
Head Loss ◽  
Local Entropy ◽  
Flow Losses ◽  
Loss Coefficients ◽  
Local Entropy Generation

Losses in a flow field due to single conduit components often are characterized by experimentally determined head loss coefficients K. These coefficients are defined and determined with the pressure as the critical quantity. A thermodynamic definition, given here as an alternative, is closer to the physics of flow losses, however. This definition is based upon the dissipation of mechanical energy as main quantity. With the second law of thermodynamics this dissipation can be linked to the local entropy generation in the flow field. For various conduit components K values are determined and physically interpreted by determining the entropy generation in the component as well as upstream and downstream of it. It turns out that most of the losses occur downstream of the components what carefully has to be taken into account when several components are combined in a flow network.

scholarly journals Physical modelling of energy losses at surcharged three-way junction manholes in drainage system

2021 ◽  
Author(s):  
Q. Li ◽  
J. Xia ◽  
M. Zhou ◽  
S. Deng ◽  
H. Zhang ◽  
...  
Keyword(s):  
Energy Loss ◽  
Flow Structure ◽  
Water Depth ◽  
Drainage System ◽  
Physical Modelling ◽  
Head Loss ◽  
Geometrical Parameters ◽  
Flow Discharge ◽  
Discharge Ratio ◽  
Loss Coefficients

Abstract Motivated by the observation that vortex flow structure was evident in the energy loss at the surcharged junction manhole due to changes of hydraulic and geometrical parameters, a physical model was used to calculate energy loss coefficients and investigate the relationship between flow structure and energy loss at the surcharged three-way junction manhole. The effects of the flow discharge ratio, the connected angle between two inflow pipes, the manhole geometry, and the downstream water depth on the energy loss were analyzed based on the quantified energy loss coefficients and the identified flow structure. Moreover, two empirical formulae for head loss coefficients were validated by the experimental data. Results indicate that the effect of flow discharge ratio and connected angle are significant, while the effect of downstream water depth is not obvious. With the increase of the lateral inflow discharge, the flow velocity distribution and vortex structure are both enhanced. It is also found that a circular manhole can reduce local energy loss when compared to a square manhole. In addition, the tested empirical formulae can reproduce the trend of total head loss coefficient.

On symmetric intrusions in a linearly stratified ambient: a revisit of Benjamin's steady-state propagation results

2021 ◽  
Vol 929 ◽  
Author(s):  
M. Ungarish
Keyword(s):  
Steady State ◽  
Control Volume ◽  
Gravity Current ◽  
Head Loss ◽  
Stability Criteria ◽  
Ambient Fluid ◽  
Height Ratio ◽  
Stagnation Line ◽  
Volume Analysis ◽  
State Propagation

Previous studies have extended Benjamin's theory for an inertial steady-state gravity current of density $\rho _{c}$ in a homogeneous ambient fluid of density $\rho _{o} < \rho _{c}$ to the counterpart propagation in a linearly stratified (Boussinesq) ambient (density decreases from $\rho _b$ to $\rho _{o}$ ). The extension is typified by the parameter $S = (\rho _{b}-\rho _{o})/(\rho _{c}-\rho _{o}) \in (0,1]$ , uses Long's solution for the flow over a topography to model the flow of the ambient over the gravity current, and reduces well to the classical theory for small and moderate values of $S$ . However, for $S=1$ , i.e. $\rho _b = \rho _c$ , which corresponds to a symmetric intrusion, various idiosyncrasies appear. Here attention is focused on this case. The control-volume analysis (balance of volume, mass, momentum and vorticity) produces a fairly compact analytical formulation, pending a closure for the head loss, and subject to stability criteria (no inverse stratification downstream). However, we show that plausible closures that work well for the non-stratified current (like zero head loss on the stagnation line, or zero vorticity diffusion) do not produce satisfactory results for the intrusion (except for some small ranges of the height ratio of current to channel, $a = h/H$ ). The reasons and insights are discussed. Accurate data needed for comparison with the theoretical model are scarce, and a message of this paper is that dedicated experiments and simulations are needed for the clarification and improvement of the theory.

Experiments and Modeling of the Hydraulic Resistance of In-Line Square Pin Fin Heat Sinks With Top By-Pass Flow

2003 ◽  
Author(s):  
Mario Urdaneta ◽  
Alfonso Ortega ◽  
Russel V. Westphal
Keyword(s):  
Static Pressure ◽  
Heat Sinks ◽  
Pressure Measurements ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Full Development ◽  
Background Data ◽  
Physical Insight ◽  
Loss Coefficients ◽  
Insight Into

Extensive experiments were performed aimed at obtaining physical insight into the behavior of in-line pin fin heat sinks with pins of square cross-section. Detailed pressure measurements were made inside an array of square pins in order to isolate the inlet, developing, fully developed, and exit static pressure distributions as a function of row number. With this as background data, overall pressure drop was measured for a self-consistent set of aluminum heat sinks in side inlet side exit flow, with top clearance only. Pin heights of 12.5 mm, 17.5 mm, and 22.5 mm, pin pitch of 3.4 mm to 6.33 mm, and pin thickness of 1.5 mm, 2 mm and 2.5mm were evaluated. Base dimensions were kept fixed at 25 × 25 mm. In total, 20 aluminum heat sinks were evaluated. A “two-branch by-pass model” was developed, by allowing inviscid acceleration of the flow in the bypass section, and using pressure loss coefficients obtained under no bypass conditions in the heat sink section. The experimental data compared well to the proposed hydraulic models. Measurements in the array of pins showed that full development of the flow occurs after nine rows, thus indicating that none of the heat sinks tested could be characterized as fully-developed.

scholarly journals Holistic Design Approach of a Throttled Surge Tank: The Case of Refurbishment of Gondo High-Head Power Plant in Switzerland

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3440
Author(s):  
Mona Seyfeddine ◽  
Samuel Vorlet ◽  
Nicolas Adam ◽  
Giovanni De Cesare
Keyword(s):  
Power Plant ◽  
Transient Flow ◽  
Holistic Approach ◽  
Head Loss ◽  
Surge Tank ◽  
3D Numerical Modeling ◽  
Head Loss Coefficient ◽  
Loss Coefficients ◽  
High Head ◽  
Modeling Strategy

In order to increase the installed capacity, the refurbishment of Gondo high-head power plant required a modification of the existing surge tank by installing a throttle at its entrance. In a previous study, the geometry of this throttle was optimized by physical modeling to achieve the target loss coefficients as identified by a transient 1D numerical analysis. This study complements previous analyses by means of 3D numerical modeling using the commercial software ANSYS-CFX 19 R1. Results show that: (i) a 3D computational fluid dynamics (CFD) model predicts sufficiently accurate local head loss coefficients that agree closely with the findings of the physical model; (ii) in contrast to a standard surge tank, the presence of an internal gallery in the surge tank proved to be of insignificant effect on a surge tank equipped with a throttle, as the variations in the section of the tank cause negligible local losses compared to the ones induced by the throttle; (iii) CFD investigations of transient flow regimes revealed that the head loss coefficient of the throttle only varies for flow ratios below 20% of the total flow in the system, without significantly affecting the conclusions of the 1D transient analysis with respect to minimum and maximum water level in the surge tank as well as pressure peaks below the surge tank. This study highlights the importance of examining the characteristics of a hydraulic system from a holistic approach involving hybrid modeling (1D, 3D numerical and physical) backed by calibration as well as validation with in-situ measurements. This results in a more rapid and economic design of throttled surge tanks that makes full use of the advantages associated with each modeling strategy.

CFD Challenge: Solutions Using the In-House Finite-Element-Based Solver NEWTETR

2012 ◽  
Author(s):  
Yiemeng Hoi ◽  
David A. Steinman
Keyword(s):  
Steady State ◽  
Pressure Measurements ◽  
Surface Geometry ◽  
Flow Rates ◽  
Pressure Drops ◽  
Or Groups ◽  
Giant Cerebral Aneurysm ◽  
Pulsatile Pressure ◽  
Nominal Surface

Briefly, this Challenge aims to test the sensitivity of steady and pulsatile pressure drops as predicted by different CFD solvers or groups, and ultimately against in vitro pressure measurements. The current study focuses on the Phase I of the Challenge. We simulated steady state and pulsatile pressure drops based on the nominal surface geometry and specific inlet flow rates on a giant cerebral aneurysm with proximal stenosis.

scholarly journals A Temperature-Insensitive Resonant Pressure Micro Sensor Based on Silicon-on-Glass Vacuum Packaging

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 3866 ◽  
Author(s):  
Pengcheng Yan ◽  
Yulan Lu ◽  
Chao Xiang ◽  
Junbo Wang ◽  
Deyong Chen ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Vacuum Packaging ◽  
Silicon On Insulator ◽  
Pressure Measurements ◽  
Element Analysis ◽  
Pressure Sensitive ◽  
Order Of Magnitude ◽  
Micro Sensor ◽  
Q Factors ◽  
Fitting Error

This paper presents a temperature-insensitive resonant pressure sensor, which is mainly composed of a silicon-on-insulator (SOI) wafer for pressure measurements and a silicon-on-glass (SOG) cap for vacuum packaging. The variations of pressure under measurement bend the pressure sensitive diaphragm and regulate the intrinsic frequencies of the resonators in the device layer. While, variations of temperature cannot significantly change the intrinsic frequencies of the resonators, due to the SOG cap to offset generated thermal stress. Numerical simulations, based on finite element analysis, were conducted to calculate the residual thermal stress and optimize the sensing structures. Experimental results show that the Q-factors of the resonators are higher than 16,000, with a differential pressure sensitivity of 11.89 Hz/kPa, a nonlinearity of 0.01% F.S and a low fitting error of 0.01% F.S with the pressure varying from 100 kPa to 1000 kPa. In particular, a temperature sensitivity of ~1 Hz/°C was obtained in the range of −45 °C to 65 °C, which is one order of magnitude lower than the previously reported counterparts.

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