scholarly journals Perbandingan Hasil Pemodelan Aliran Satu Dimensi Unsteady Flow dan Steady Flow pada Banjir Kota

2016 ◽  
Vol 21 (1) ◽  
pp. 35 ◽  
Author(s):  
Andreas Tigor Oktaga ◽  
Suripin Suripin ◽  
Suseno Darsono
Keyword(s):  
Unsteady Flow ◽  
Water Level ◽  
Steady Flow ◽  
River Flow ◽  
Uniform Flow ◽  
Flood Water ◽  
One Dimensional ◽  
Advantages And Disadvantages ◽  
Dimensional Flow ◽  
The Stability

One dimensional flow is often used as a flood simulation for the planning capacity of the river. Flood is a type of unsteady non-uniform flow, that can be simulated using HEC-RAS. HEC-RAS software is often used for flood modeling with a one-dimensional flow method. Unsteady flow modeling results in HEC-RAS sometimes refer to error and warning due to unstable analysis program. The stability program among others influenced bend in the river flow, the steep slope of the river bottom, and changes in cross-section shape. Because the flood handling required maximum discharge and maximum flood water level, then a steady flow is often used as an alternative to simulate the flood flow. This study aimed to determine the advantages and disadvantages of modeling unsteady non-uniform and steady non-uniform flow. The research location in the Kanal Banjir Barat, in the Semarang City. Hydraulics modeling uses HEC-RAS 4.1 and for discharge the plan is obtained from the HEC-HMS 3.5. Results of the comparison modeling hydraulics the modeling of steady non-uniform flow has a tendency water level is higher and modeling of unsteady non-uniform flow takes longer to analyze. Results of the comparison the average flood water level maximun is less than 15%  (± 0,3 meters), that is 0.27 meters (13.16%) for Q50, 0.25 meters (11.56%) for Q100, dan 0.16 meters (4.73%) for Q200. So the modeling steady non-uniform flow can still be used as a companion version the modeling unsteady non-uniform flow.

Comparison of Unsteady Flow Discharge Coefficients for Sharp-Edged Orifices with Steady Flow Values

1966 ◽  
Vol 8 (3) ◽  
pp. 322-329 ◽  
Author(s):  
G. H. Trengrouse ◽  
B. W. Imrie ◽  
D. H. Mal
Keyword(s):  
Unsteady Flow ◽  
Shock Tube ◽  
Steady Flow ◽  
Pressure Measurements ◽  
Compressive Wave ◽  
Convergent Nozzle ◽  
Flow Discharge ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Discharge Coefficients

A simple theory, based on quasi-steady, one-dimensional flow arguments, is presented for the reflection of a compressive wave in air in a pipe when incident upon a coaxial, convergent nozzle situated at the end of the pipe. Preliminary shock-tube experiments using quadrant arc nozzles confirm the validity of the theory, and thus enable it to be used to predict the discharge coefficients of sharp-edged orifices from pressure measurements taken in the pipe in the immediate vicinity of the orifices during further shock-tube experiments. Steady flow discharge coefficients measured experimentally differ from the unsteady flow values by a maximum of 7 per cent.

scholarly journals Experimental study on water level and absorption capacity in a radial well flow in a loess area

2018 ◽  
Vol 19 (5) ◽  
pp. 1313-1321
Author(s):  
Xuezhen Zhang ◽  
Aidi Huo ◽  
Jucui Wang
Keyword(s):  
Unsteady Flow ◽  
Water Absorption ◽  
Water Level ◽  
Steady Flow ◽  
Flow Injection ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Analysis Method ◽  
Semi Empirical ◽  
Radial Well

Abstract In this paper, the theoretical basis for flow calculation in an injection well was discussed. It proposed that the flow rate of an injection well could be calculated referring to pumping theory and method. A mathematical model of the rising curve of water level around a radial well was established and the equation for calculating the rising curve was given. The calculation equations selected for the water absorption capacity of injection wells were explained and examples were verified and compared. The results indicated that, under the same injection conditions, the water level value calculated by the analysis method was slightly larger, but the error between the analysis method and the semi-theoretical and semi-empirical methods was small. In the processes of steady flow injection and unsteady flow injection, there was a small difference of water absorption capacity, and the former was slightly larger. The measured values of water absorption capacity were only about one-third of the calculated values based on pumping theory. Overall, the analytical solution method for predicting the rising curve of water level has priority in well injection. The semi-theoretical and semi-empirical equation for calculating water absorption capacity sifted first has priority in steady flow injection, the equation sifted second has priority in unsteady flow injection.

Stability limits of unsteady open capillary channel flow

2008 ◽  
Vol 600 ◽  
pp. 271-289 ◽  
Author(s):  
ALEKSANDER GRAH ◽  
DENNIS HAAKE ◽  
UWE ROSENDAHL ◽  
JÖRG KLATTE ◽  
MICHAEL E. DREYER
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Flow Rate ◽  
Stability Theory ◽  
Unstable Flow ◽  
Free Surfaces ◽  
Capillary Channel ◽  
Choked Flow ◽  
The Stability ◽  
Stable Flow

This paper is concerned with steady and unsteady flow rate limitations in open capillary channels under low-gravity conditions. Capillary channels are widely used in Space technology for liquid transportation and positioning, e.g. in fuel tanks and life support systems. The channel observed in this work consists of two parallel plates bounded by free liquid surfaces along the open sides. The capillary forces of the free surfaces prevent leaking of the liquid and gas ingestion into the flow.In the case of steady stable flow the capillary pressure balances the differential pressure between the liquid and the surrounding constant-pressure gas phase. Increasing the flow rate in small steps causes a decrease of the liquid pressure. A maximum steady flow rate is achieved when the flow rate exceeds a certain limit leading to a collapse of the free surfaces due to the choking effect. In the case of unsteady flow additional dynamic effects take place due to flow rate transition and liquid acceleration. The maximum flow rate is smaller than in the case of steady flow. On the other hand, the choking effect does not necessarily cause surface collapse and stable temporarily choked flow is possible under certain circumstances.To determine the limiting volumetric flow rate and stable flow dynamic properties, a new stability theory for both steady and unsteady flow is introduced. Subcritical and supercritical (choked) flow regimes are defined. Stability criteria are formulated for each flow type. The steady (subcritical) criterion corresponds to the speed index defined by the limiting longitudinal small-amplitude wave speed, similar to the Mach number. The unsteady (supercritical) criterion for choked flow is defined by a new characteristic number, the dynamic index. It is based on pressure balances and reaches unity at the stability limit.The unsteady model based on the Bernoulli equation and the mass balance equation is solved numerically for perfectly wetting incompressible liquids. The unsteady model and the stability theory are verified by comparison to results of a sounding rocket experiment (TEXUS 41) on capillary channel flows launched in December 2005 from ESRANGE in north Sweden. For a clear overview of subcritical, supercritical, and unstable flow, parametric studies and stability diagrams are shown and compared to experimental observations.

scholarly journals Efektifitas Pengendalian Banjir dengan Embung: Studi Kasus Taman Firdaus Universitas Sriwijaya

CANTILEVER ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 57-62
Author(s):  
Deny Ferdian ◽  
Anis Saggaff ◽  
Sarino
Keyword(s):  
Water Level ◽  
Economic Activities ◽  
Wet Season ◽  
Small Reservoir ◽  
Flood Water ◽  
One Dimensional ◽  
Catchment Areas ◽  
Retention Basin

Flood is triggered by a decrease in catchment areas due to an increase in population, activities, and land requirements, both for settlements and economic activities. The flood occurs annually during the wet season at downstream of the campus of Sriwijaya University. In 2019, the downstream swampy land of about 100 ha was excavated and functioned as a retention basin or small reservoir called Embung. The reservoir at Taman Firdaus, Sriwijaya University, was designed by using spillway's top elevation at +5.00m. The objective of the research was to analyze the effectivity of the reservoir on the flood water level of the Kelekar river. One dimensional modelling was used to model the hydraulic routing through small reservoir and Kelekar river. Based on the results of the modeling, it can be seen that the reservoir at Taman Firdaus Universitas Sriwijaya could hold water as much as 1.446.409,39 m3, and lower the flood water level in the Kelekar River by approximately 1 to 1.5 meters.

Study of self-similar and steady flows near singularities

1970 ◽  
Vol 315 (1523) ◽  
pp. 569-584 ◽  
Keyword(s):  
Steady Flow ◽  
Gas Dynamics ◽  
Integral Curve ◽  
Order Partial Differential Equation ◽  
Steady Flows ◽  
Sonic Point ◽  
One Dimensional ◽  
Self Similar ◽  
The Stability ◽  
Radiation Gas Dynamics

One-dimensional steady state flow or a self-similar flow is represented by an integral curve of the system of ordinary differential equations and, in many important cases, the integral curve passes through a singular point. Kulikovskii & Slobodkina (1967) have shown that the stability of a steady flow near the singularity can be studied with the help of a simple first-order partial differential equation. In § 2 of this paper we have used their method to study steady transonic flows in radiation-gas-dynamics in the neighbourhood of the sonic point. We find that all possible one-dimensional steady flows in radiation-gas-dynamics are locally stable in the neighbourhood of the sonic point. A continuous disturbance on a steady flow, while decaying and propagating, may develop a surface of discontinuity within it. We have determined the conditions for the appearance of such a discontinuity and also the exact position where it appears. In §3 we have shown that their method can be easily generalized to study the stability of self-similar flows. As an example we have considered the stability of the self-similar flow behind a strong imploding shock. In this case we find that the flow is stable with respect to radially symmetric disturbances.

Paper 25: Unsteady Compressible Flow in a Pipe with a Non-Return Disc Valve

1967 ◽  
Vol 182 (8) ◽  
pp. 241-249
Author(s):  
K. S. M. I. Kaddah ◽  
D. Woollatt
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Viscous Friction ◽  
Equation Of Motion ◽  
Disc Displacement ◽  
Reasonable Accuracy ◽  
One Dimensional ◽  
Spring Force ◽  
Steady Flow Condition ◽  
Displacement Diagram

A simple non-return disc valve was tested in a pipe in which an unsteady flow was produced. The valve was tested with its disc fixed in position and was also tested with the disc controlled by a spring. Records were taken of the unsteady pressure diagrams at various points in the pipe and the disc displacement diagram. To obtain the boundary conditions required for the unsteady flow calculation, it was first necessary to examine the flow in the valve under steady flow condition. The results of this investigation are briefly described. It was found that the disc displacement diagram in unsteady flow can be calculated with reasonable accuracy from the pressure drop across the valve by integrating the equation of motion of the disc numerically. The equation of motion contains terms for the inertia of the disc, the spring force, and the gas force. Viscous friction damping forces were negligible for this valve. Once the disc displacement is known, the pressure diagram can be calculated using the steady flow values for the pressure loss across the valve and the normal methods for one-dimensional unsteady flow calculations.

scholarly journals Comparative Study of One Dimensional and Two Dimensional Steady Surface Flow Analysis

2016 ◽  
Vol 2 ◽  
pp. 15
Author(s):  
Laxmi Bhakta Maharjan ◽  
Narendra Man Shakya
Keyword(s):  
Steady Flow ◽  
Water Surface ◽  
River Flow ◽  
Flow Analysis ◽  
Flood Plain ◽  
Surface Flow ◽  
Accurate Information ◽  
One Dimensional ◽  
Maximum Variation ◽  
Prismatic Channel

<p>Determination of actual water surface is required for design of hydraulic structures, reservoirs, flood plain management, and flood forecasting. Classical approach of analyzing the river flow using one dimensional flow analysis cannot provide the accurate information of water surface for different return period floods. So, both 1D and 2D steady surface flow analysis in prismatic channel and non-prismatic channel were done using models like HEC-RAS, FESWMS-2DH, GIS, and HECGEORAS to compare the results and recommended to select the best among these two flow analyses. Analysis of result showed that in prismatic channel, the water surface elevations obtained from 1D and 2D steady flow analysis for discharge Q=10cft/s were almost similar with maximum variation of 0.33ft. But in case of non-prismatic channel, the results of water surface elevations from 1D and 2D steady flow analysis for discharge Q = 5000cft/s and 9430cft/s were not similar and the maximum variation of 1.36ft and 1.75ft were found for two discharges respectively. 1D steady flow analysis is acceptable for prismatic channel except at bend which may require 2D analysis. But flow in non-prismatic channel requires 2D steady flow analysis for precise water surface elevation.</p><p><strong>Journal of Advanced College of Engineering and Management,</strong> Vol. 2, 2016, Page: 15-30 </p>

scholarly journals INVESTIGATING THE STABILITY OF LONG ONE- DIMENSIONAL WAVES IN A SLOPING RUNOFF

World Science ◽  
2020 ◽  
Vol 1 (1(53)) ◽  
pp. 18-22
Author(s):  
Otar Natishvili ◽  
Irakli Kruashvili ◽  
Irma Inashvili
Keyword(s):  
Free Surface ◽  
Soil Erosion ◽  
Unsteady Flow ◽  
Shallow Water ◽  
Flow Process ◽  
Variable Flow ◽  
One Dimensional ◽  
Continuous Waves ◽  
The Stability ◽  
The Way

The paper is dedicated to the problem of the influence of waves in shallow-water slope flows on the intensity of soil erosion that has not been considered earlier. The stability of one-dimensional continuous waves on the free surface of the sloping runoff is analyzed, both at constant, and with the variable flow along the way. Attention is drawn towards the unsteady flow process and the shape of the free surface in various planes.

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