Introducing a new computer code, H-Hammer, to solve fluid transients in pipe flow

Sudden change of flow conditions in a pipeline may cause the flow to become time dependent and would start an undesirable physical phenomenon called water hammer. These sudden changes can be caused by variety of scenarios and some of them include valve operations (opening or closing), sudden power loss at pump stations and load rejections or load acceptance at the turbines, etc. Because of its very costly and sometimes deadly consequences, it is quite important that transient scenarios be considered for pipe systems at design stage to ensure safety and longevity of them. The present study is an attempt to develop a comprehensive computer software that is capable of simulating, analyzing and solving most commonly encountered fluid transient events. The code developed, titled as H-Hammer, is already capable of using many boundary conditions to tackle a large variety of problems involving fluid transients. Within the code, the Method of Characteristics (MoC) are used to solve the basic unsteady pipe flow equations. The code utilizes AutoCAD, Visual Basic 6.0 and MS Excel all together for the purpose of analyses. The accuracy of the software was tested by solving some existing problems offered in the textbooks written by those who contributed significantly in the fluid transient area. Comparisons of the results show that the results of the developed software is in good agreement with the solutions given in those books. Keywords: Transient Scenarios, Water Hammer, Pipe Flow, Method of Characteristics, Computer Cod

Developing empirical formulae for scour depth in front of Inclined bridge piers

Neka istraživanja predlažu različite empirijske korelacije kako bi se predvidjela dubina podlokavanja ispred nagnutih stupova mosta kroz regresijsku analizu dobivenu laboratorijskim mjerenjima zbog složenih mehanizama toka oko nagnutih stupova mosta. Međutim, kako su se te korelacije razvile za određeni skup podataka, opća je jednadžba i dalje potrebna da bi se točno predvidjela dubina podlokavanja ispred nagnutih stupova mosta. Glavni je cilj istraživanja razviti opću jednadžbu kako bi se predvidjela dubina podlokavanja ispred nagnutih stupova mosta kroz višeslojni perceptron (MLP) i tehnike neuronske mreže s radijalnim baznim funkcijama (RBNN). Eksperimentalni skupovi podataka koji se primjenjuju u ovom istraživanju skupljeni su se iz prijašnjih istraživanja. Jednadžba za dubinu podlokavanja prednjeg stupa koristi se primjenom pet varijabl. Rezultati analiza umjetne neuronske mreže (ANN) otkrivaju da su modeli RBNN i MLP omogućili preciznija predviđanja nego prethodne empirijske korelacije kad su u pitanju izlazne varijable. Prema tome, predlažu se analitičke jednadžbe dobivene RBNN i MLP modelima za točno predviđanje dubine podlokavanja ispred nagnutih stupova mosta. Štoviše, na temelju rezultata analize osjetljivosti utvrđuje se da je na dubinu podlokavanja ispred prednjih i stražnjih stupova najviše utjecao kut nagiba, odnosno intenzitet toka.Because of the complex flow mechanism around inclined bridge piers, previous studies have proposed different empirical correlations to predict the scouring depth in front of piers, which include regression analysis developed from laboratory measurements. However, because these correlations were developed for particular datasets, a general equation is still required to accurately predict the scour depth in front of inclined bridge piers. The aim of this study is to develop a general equation to predict the local scour depth in front of inclined bridge pier systems using multilayer perceptron (MLP) and radial-basis neural-network (RBNN) techniques. The experimental datasets used in this study were obtained from previous research. The equation for the scour depth of the front pier was developed using five variables. The results of the artificial neural-network (ANN) analyses revealed that the RBNN and MLP models provided more accurate predictions than the previous empirical correlations for the output variables. Accordingly, analytical equations derived from the RBNN and MLP models were proposed to accurately predict the scouring depth in front of inclined bridge piers. Moreover, from the sensitivity analyses results, we determined that the scour depths in front of the front and back piers were primarily influenced by the inclination angle and flow intensity, respectively

Afet yönetimi için baraj yıkılma analizleri

Numerical failure simulations of Kestel dam were performed under different scenarios. The numerical model employed was developed by Fread, D.L., and called DAMBRK. In the simulations, it was assumed that a breaching started, within the dam body soon after the maximum possible flood hydrograph entered the dam reservoir and caused the water to spill over the dam crest due to insufficient capacity of the spillway. Peak flood discharges, peak flood elevations and flood arrival times at preselected six cross-sections downstream of the dam were determined. Regions affected most adversely were found to be those closest to the dam site

Waterhammer analyses of the Camlidere-Ivedik Pipeline

In the present study, a widely used mathematical method for unsteady flows in closed conduits such as pipes and/or tunnels, called the Method of Characteristics (M. O. C.) was employed to perform water-hammer analysis of the pipelines extending from the Camlidere dam to the Ivedik water treatment plant in Ankara. Both of the existing parallel pipe lines, are formed by various steel pipes, reinforced concrete pipes and concrete lined tunnels connected in series and having different material characteristics in roughness, diameters and lengths. To take into account all of these various characteristics of the pipelines, the unsteady flow equations consisting of the interpolation feature were used when employing the M.O.C. An algorithm was developed which was incorporated into an existing computer model, written in FORTAN language. By way of this program, the numerical simulations of water hammer problem under desired scenarios were performed. As a result, closure durations were recommended for the pipe fracture safety devices planned to be located at certain places and to be put into operation automatically in case of emergency, without causing excessive pressures in the lines

Hydrodynamics of a transient slug motion in an empty pipe system

Liquid slugs (water pockets) are propelled into an empty pipe under various driving pressures; the pipe's extension ends at an elbow whereon the slugs impact and disintegrate. Dynamic pressures recorded at various locations along the system indicate the complex and somewhat random structure of the transient. High-speed movies of the evolving slug just prior to impact show that significant air entrainment and breakup of the slug occurs. A simplified analytical model is developed to predict the slug dynamics; in spite of the complexity of the flow, reasonable comparisons of peak pressures and impulse loads at the elbow are obtained and are in parallel with results reported in an earlier study

Çınarcık Barajının Sanal Yıkılma Analizleri

Bu çalışmada, önceden belirlenmiş bir dizi senaryo çerçevesinde sanal bir baraj yıkılmasının olası etkilerini bir durum çalışması kapsamında görmek amacı ile analizler yapılmıştır. Çalışmanın konusu Türkiye’nin Bursa İli’nde yer alan Çınarcık Barajıdır. Belirli kritik kıstaslar aşıldığında barajın yıkılmasının tetiklendiği varsayılmaktadır. Dolayısıyla analizler, yıkılmanın ardından gerçekleşen olumsuz sonuçlara odaklanmakta ve barajın mansabındaki taşkın düzeyini zamana bağlı olarak öngörmeye çalışmaktadır. Analizler sırasında Çınarcık Barajı’nın mansabında gerçekleşen akış profillerini, su yüzü kotlarını ve deşarj değerlerini, tanımlanan senaryolar çerçevesinde uzamsal ve zamansal olarak tahmin etmek amacıyla, ABD’de “National Weather Service” tarafından geliştirilmiş olan FLDWAV yazılımı kullanılmıştır. Bu analizler esas alınarak, gösterge düzeyinde taşkın haritaları ve bunlara göre risk altında olan yerleşim yerleri tespit edilmiş olup, ayrıca yıkılma öncesinde alınması gerekli bazı önlemler de önerilmektedi

Effects of inclination of bridge piers on scouring depth

For a safe design of a bridge pier footing, it is important to estimate the maximum depth of scour as accurately as possible. The aim of this experimental study is to investigate the effects of inclination of bridge piers on local scour depths around bridge piers. Single circular piers inclined toward the downstream direction were founded in a uniform bed material. Near threshold conditions were employed. The results of this study indicate that the local scour depth decreases as the inclination of the pier increases