Skema Implisit untuk Penyelesaian Propagasi Gelombang Aliran Terbuka Satu Dimensi.

Kata kunci: Skema implisit - Propagasi - Gelombang Aliran Terbuka Satu Dimensi

Model Numerik Elemen Hingga 3d untuk Sebaran Gelembung Udara Dalam Air = Finite Element Numerical Modeling Of Air Bubble Spreading In Water

ABSTRACT The motion and spreading of air bubble highly affect the effectiveness and efficiency of aeration process. This research developed a numerical model to simulate and to predict the motion and the spreading of air bubble in an aerator column. In this approach, modeling of aeration process considers air bubbles as a material that transported and dispersed in the water. The model assumed that bubble diameter could be ranged in their size. The dynamics of air bubbles motion and spreading is modeled as convection-diffusion equation and implemented only for one diameter range. Petrov-Galerkin Finite Element Method on 20 nodes quadratic brick element is used to solve this equation. To develop the model, velocity and diffusion coefficient was determined based on the results of the investigation of air bubble motion and spreading in the column aerator. From the modeling results of the motion and spreading of air bubble, the relation between diffusion coefficient and the air bubble concentration with 2 It/mnt sparger discharge was found, k=0,12(C-0,0006), where k is diffusion coefficient and C is air bubble concentration. To show the performance of the model, a comparison to the result of the air bubble motion investigation was carried out. The numerical model that has been obtained is capable in simulating the phenomenon of the dynamics of air bubble motion and spreading. Keywords : Air Bubble Spreading, Convection-Diffusion, and Finite Element Method

Kontribusi Kemampuan Juru Pintu Pada Pengelolaan Pembagian air Irigasi

ABSTRAK Jaringan irigasi pada kenyataannya selalu mempunyai ketidakcocokkan dengan perancangan awal maupun adanya perubahan kondisi bangunan fisik selama pengoperasian yang sudah berlangsung. Ketidaksesuaian ini dapat pula terjadi pada perangkat lunak pengoperasiannya, misalnya rencana pemberian air yang terlalu jauh dari kebiasaan pengelolaan pemberian air sebelum ada jaringan teknis, atau. RPA I yang tidak mungkin dilaksanakan karena penyimpangan keadaan fisik jaringan tersebut di atas. Perubahan-perubahan yang terjadi pada pintu pembagi dan alat ukur debit yang dapat menimbulkan kesulitan pengaturan dan pengukuran oncoran air adalah hal yang paling sering terjadi. Juru pintu yang merupakan salah satu bagian dari mata ran tai pengelola irigasi sering mendapat beban yang paling besar oleh adanya ketidaksesuaian tersebut di atas. Tinjauan ini yang bertitik berat pada studi kasus di Proyek Irigasi CITAGAMPOR membahas peranan juru pintu dalam pengelolaan pembagian air irigasi, evaluasinya dan kemungkinan perbaikan tata kerjanya

Penyusunan Model Elemen Hingga Interaksi Persamaan Aliran dengan Persamaan Sebaran Udara

Aeration process is one of water treatment processes. The process consists of two physical phenomena, flow, and spreading of air bubble. This research has developed a finite element model for three-dimensional flow and spreading of air bubble. The flow equation employs Navier-Stokes equation. The spreading of air bubble is modeled as convection-diffusion equation. The Navier-Stokes and the spreading of air bubble equation are combined by Navier-Stokes equation with additional new term, which shows the accelerated flow caused by the air bubble moves. The Navier-Stokes equation was solved in four stages, i.e., Taylor Galerkin convection approximation, viscous prediction, pressure correction and velocity correction stages. Galerkin Standard method was used to solve the spreading of air bubble equation. Quadratic brick finite elements with 20 nodes were used on the geometry. To show performance model, comparison to the result of air bubble investigation was carried out. The numerical model that has been obtained is capable of simulating the phenomena of air bubble spreading and flow. The numerical stability analyses showed that the numerical scheme of convection and diffusion equation based on Galerkin is stable for Courant Number £ 0.01 and Peclet Number 125

Studi model intrusi air asin di sungai juana hilir.

Penutupan Pintu Wilalung di sungai Serang dikhawatirkan akan mengurangi debit di sungai Juana yang akan memberi kesempatan intrusi air laut ke daerah pertanian. Sebuah studi telah dilaksanakan untuk mengetahui jarak jangkau intrusi air asin ini dan muara dengan beberapa penelitian lapangan. Dan untuk menghitung parameter-parameternya, hasil penelitian lapangan tersebut digunakan dalam hitungan angkutan massa dengan model stasioner. Parameter-parameter yang diperoleh diharapkan dapat dipakai untuk penelitian selanjutnya

Unit Hydrograph Modeling using Geomorphological Instantaneous Unit Hydrograph (GIUH) Method

Flood forecasting at Wonogiri Reservoir is restricted on the availability of hydrologic data due to limited monitoring gauges. This issue triggers study of unit hydrograph modeling using Geomorphological Instantaneous Unit Hydrograph (GIUH) which is based on Geographic Information System (GIS). Analysis of physical watershed parameters was conducted on Digital Elevation Model (DEM) data using software Watershed Modeling System (WMS) 10.1 and ArcGIS. Nash model and S-curve method were used to process triangular GIUH into hourly Instantaneous Unit Hydrograph (IUH) and Unit Hydrograph (UH) and then was compared with the observed UH of Collins method. A sensitivity analysis was conducted on parameter of RL and Nash-model k. Evaluation of accuracy of the simulated GIUH runoff hydrograph was also conducted. The GIUH model generated UH with smaller peak discharge Qp, also slower and longer of tp and tb values than the observed UH. Accuracy test of the simulated GIUH runoff hydrograph using Nash-Sutcliffe Efficiency (NSE) shows that Keduang watershed gives a satisfying result, while Wiroko watershed gives less satisfactory result. The inaccuracies occur due to limited flood events used to derive the observed UH and stream tributaries that were not properly modeled based on Strahler method

Kajian Pengaruh Konfigurasi Krib Terhadap Pola Arus Di Belokan

ABSTRAK Current pattern control along channel bend can be done technically by proper lay-out of groyne at the channel banks with certain configuration. To get the optimal configuration of the groyne, current patterns downstream of the groyne with different lay-outs were analyzed quantitatively and qualitatively, Observation and evaluation of the effect of groyne lay-out to the current pattern along the channel bend was conducted by two approach, i,eâ physical modeling and mathematical modeling. Numerical simulation and physical model runs were conducted in a generic channel. Observation of hydraulic characteristics of flow at laboratory was done by particle image velocimetry method. Current pattern simulation was done with the BOSS SMS - FESWMS software module. This module is a 2-D depth average mathematical model. To get accurate simulation, the RMS of deviation of the numerical result from the measurement result at several locations was used as the indicator parameter in the calibration and the verification process. Quantity analysis of current pattern as hydraulic respons of the existence of the groyne was based on velocity distribution skewness at selected cross sections. The results showed that the variation of groyne length projection (17B=0,087-0,260) gave the change of the sk value by 31,4 - 325,8%, the variation of groyne setting direction (a/180=0,33-.0,67) gave the change of the sk value by 0,5 47,7%, and the channel\u27s Reynolds number (Rech.7,97x104-1,51x105) gave the change of the sk value by 0,2 - 12,0%. The perpendicular groyne lay-out to the bank gave the strongest effect to change of velocity was compared with the other configuration (in comparison with the channel without groyne), whether change of velocity at downstream cross section at inner bend side (10,95 - 53,88%) or at upstream cross section at outer bend side (-13,12 - -51,77%). Keywords : current pattern, configuration of the groyne, bend, skewness

Verifikasi Dan Kalibrasi Model Matematis Aliran Permukaan Dua Dimensi (Rma2), Pengaruh Eddy Viscosity Dan Kekasaran Dasar Pada Pola Aliran

The development of numerical models has provided some potentially useful engineering softwares especially for hydraulic engineering. A software called RMA2 in the BOSS SMS package is one of them that were supposed to be able to simulate 2D depth averaged surface water flow. A study has been conducted to verb the performance of the RMA2 software on flow influenced by tidal backwaters. The verification was done by comparing the result of flow simulation of dynamic backwater flow on a sinuous channel with a narrow section and the measured data on a physical model of flow on the same system. The measurement of flow velocity and flow pattern implemented particle image velocimetty method by using foam/patched floating tracer. Flow velocity data on several flow measurement stations were analysed quantitatively and the flow patterns were discussed qualitatively. The result of the study shows that the curves of velocity magnitudes on all measurement measured from the physical model and simulated by the mathematical model have very small differences. This result was achieved by implementing several zones in the computational domain with different roughness and diffusion coefficients. Both the mathematical and physical model shows similar pattern

Penyusunan Model Elemen Hingga Persamaan Navier-Stokes 3 Dimensi Untuk Aliran Tak Mampat

ABSTRAK Fluid dynamics modeling is important for hydraulic structure design or any process which involes flow like transport of pollutant. A finite element model for 3-D unsteady and incompressible flow is developed. The fundamental equations are the momentum (Navier-Stokes) and the continuity equations. These equations are written in the primitive variables of velocity components and pressure. The numerical scheme employs time-splitting method. It consists of four stage solution procedures within a time step, i.e., Taylor-Galerkin convective approximation, viscous prediction, pressure correction, and velocity correction. The velocity-pressure solution based on the quadratic velocity and linear pressure interpolation. To show performance of the model, comparison to the analytical solution on simple cases and comparison to other researchers\u27s results was performed. The numerical simulations show that the numerical scheme based on Taylor-Galerkin pure convection equation is stable for Courant number S 0,39. The numerical scheme which involves convection and viscous terms is stable for certain range of Courant (Cr) and Peclet (Pe) number, for Peclet number 0 7 Courant number remains constant on 0,39. Keywords : Navier-Stokes equation, incompressible flow, finite element, Taylor-Galerki

Pengembangan Metode Pengukuran Medan Kecepatan Aliran Dengan Metode Bayangan Partikel

Flow velocity measurement is one of the very important aspect in the field of hydraulics. Until today, the commom method used in measuring flow velocity is limited to one point measurement. In order to get velocity pattern in a single measurement, multi point velocity measurement methods such particle image and tracking methods have to be developed A study for the development of the instrument based on particle image method has been conducted. The developed measurement method was validated by applying it on velocity field measurement of two steady uniform flow cases, they were: flow in normal straight flume and down-stream flow of broad crested weir. Collecting and analyzing data procedure were as follows: setting up flow cases and inserting particles into water flow, lighting the flow and recording image by developed instrument, photographic (studio) processing, photo scanning, reading pixel brightness data, transforming pixel data into velocity flow data, visualizing velocity vectors, and validating data by comparing them with data collected by a volumetric calibrated Mini Propeller velocimeter. The results indicate that data collected by developed measurement method were comparable and relevant to data collected by the volumetric calibrated Mini Propeller. The mean velocity profile measured by developed measurement method in straight flume was 8-14 cm/s, meanwhile that of Mini Propeller was 9-13.5 cm/s. Measurement error between data obtained by those two methods was 4.8 percent (RMS= 0.5635 cm/s). In case of downstream flow of a broad crested weir, the data were 0.97-2.24 cm/s for developed measurement method and 0.77-2.19 cm/s for standard measurement. Measurement error was 7.7 percent (RMS=0.1228 cm/s). Furthermore, by using the measurement method developed in this research, location, magnitude, and direction of the velocity vectors distributed on the velocity field would be available simultaneously