@article { author = {Nezafatkhah, S. and Bayat, H.O.}, title = {An Investigation into the Effects of the Experimentation Scale Upon Unsteady Non-Darcy Flows Through Rubble Mound Breakwaters}, journal = {Journal of Hydraulics}, volume = {3}, number = {3}, pages = {1-13}, year = {2008}, publisher = {Iranian Hydraulic Association}, issn = {2345-4237}, eissn = {2645-8063}, doi = {10.30482/jhyd.2008.85470}, abstract = {As the pore pressure within core materials in rubble mound breakwaters affect the armours stability, itis often necessary to consider scale effects when related designs call for a hydraulic model study basedon the Froude criterion. This paper describes findings of an analytical evaluation of unsteadytransitional flow regimes through coarse porous media in an attempt to develop a modelling law basedon similarities between hydraulic behaviours of the model and the prototype. A non-linear analysisapproach based on the so-called modified Forschhiemer equation has been employed in developingnecessary equations needed for scale effects assessments. It has been made clear that the grains scaleratio is not a constant and its power varies with variations of the flow regime. The extent of thevalidity of findings in enabling correct interpretation of experimental results have been examinedusing available field data published by previous researchers for rubble mound structures.}, keywords = {}, title_fa = {بررسی اثر مقیاس در مطالعه آزمایشگاهی جریان های غیردارسی غیرماندگار گذرنده از موج شکن های توده سنگی}, abstract_fa = {}, keywords_fa = {}, url = {https://jhyd.iha.ir/article_85470.html}, eprint = {https://jhyd.iha.ir/article_85470_b0f970f287ac2d861151c8960040d7a1.pdf} } @article { author = {Heidarpour, M. and Ghorbani, B. and Keykhai, M. and Pirmohamadi, R.}, title = {Effect of Slot on Stability of Riprap around Bridge Piers}, journal = {Journal of Hydraulics}, volume = {3}, number = {3}, pages = {15-28}, year = {2008}, publisher = {Iranian Hydraulic Association}, issn = {2345-4237}, eissn = {2645-8063}, doi = {10.30482/jhyd.2008.85471}, abstract = {An accepted engineering method to deal with local scouring at bridge piers is to place riprap materialaround the pier foundation. Field experience has shown that riprap stones often disappear with time,with most severe failure occurring during floods; and refilling is frequently needed to replenish thelost stones. Therefore, notice to riprap stability is necessary and has been the aim of this paper. In thisresearch, four sizes of riprap located above, the same level and below the surface of the streambed andtwo slot sizes continued to the streambed were used. Effect of presence and size of slot on riprapstability and minimum necessary dimensions for finished riprap covering have been studied. Theresults obtained in the experiments range; show that riprap is more stable when using slot and thisstability is more evident with bigger slot. The performance of the two slot sizes decreases when usingthe bigger stones. Decrease in performance of the big slot using the bigger stones is more than that ofthe small slot. Furthermore, results show that the slot decreases the finished riprap covering andconsequently the riprap volume will decrease effectively. It has been found that the riprap placedabove and below the streambed have the most and the lowest stability, respectively.}, keywords = {}, title_fa = {تاثیر شکاف پایه بر پایداری سنگ چین در اطراف پایه های استوانه ای پل ها}, abstract_fa = {}, keywords_fa = {}, url = {https://jhyd.iha.ir/article_85471.html}, eprint = {https://jhyd.iha.ir/article_85471_1f0b373fa964784bf9d8b8a379832b7b.pdf} } @article { author = {Shafai Bejestan, Mahmood and Neisi, K.}, title = {Effects of Bed Roughness Shape on the Length of Hydraulic Jump}, journal = {Journal of Hydraulics}, volume = {3}, number = {3}, pages = {29-40}, year = {2008}, publisher = {Iranian Hydraulic Association}, issn = {2345-4237}, eissn = {2645-8063}, doi = {10.30482/jhyd.2008.85472}, abstract = {In this study, effects of shape of roughness elements on the length of hydraulic jump havebeen investigated experimentally. For the purpose of this study, prismatic roughness elementswith different shapes (rectangular, triangular, circular, lozenge and hexangular) have beentested in a rectangular flume 7.5m long and 30cm wide. Experiments were performed in thehydraulic laboratory of Shahid Chamran University, Ahwaz, Iran. The roughed elements areglued on the bed of flume downstream of ogee spillways in such a way that the incomingwater jet is just above the element surface. It should be noted that in previous studies therough elements have been tested such that the incoming jet was at the same level of theelement bottom so the elements act as baffle blocks. Each rough element was tested underdifferent flow conditions. The incoming Froude number was in the range of 4.5 to 12. Duringeach test the water surface profile, the roller length and the jump length were measured. Infew tests the longitudes and vertical flow velocity were measured. The results indicate that thepresence of rough element can reduce the hydraulic jump length and the amount of thereduction depends on the Froude number and the roughness shape. The lozenge element shapewas found to produce lesser jump length (up to 40% of the smooth bed jump). Relations havebeen presented in this study to predict jump length, roller length and the amount of energywhich is dissipated. Comparison of this study with previous results reveals that using therough element can reduce the hydraulic jump as much as the block elements do, and the roughelement can not cause separation of flow which might be subject to cavitations.}, keywords = {}, title_fa = {تاثیر شکل زبری بستر بر طول پرش هیدرولیکی در کانال های مستطیلی}, abstract_fa = {}, keywords_fa = {}, url = {https://jhyd.iha.ir/article_85472.html}, eprint = {https://jhyd.iha.ir/article_85472_2a4e307d55b09dc3873ac73064f858ce.pdf} } @article { author = {Vaghefi, M. and Ghodsian, M. and Salehi Neyshabouri, S.A.A.}, title = {Experimental Study of 3D Flow Field and Scour in a 90 Degree Bend}, journal = {Journal of Hydraulics}, volume = {3}, number = {3}, pages = {41-57}, year = {2008}, publisher = {Iranian Hydraulic Association}, issn = {2345-4237}, eissn = {2645-8063}, doi = {10.30482/jhyd.2008.85473}, abstract = {Flow is affected by both the pressure gradient and the centrifugal forces in the bend of rivers and theirinteraction leads to secondary flow. In this study the flow field and scour in a 90 degree bend wereexperimentally measured. Experiments were carried out in a channel with mild curvature. A threedimensionalAcoustic Doppler Velocimeter (ADV) was used for measuring the flow field. Also, alaser bed profiler was used for measuring the variation of bed topography. The results show formationof a main secondary flow in the bend and another second secondary flow near the outer bank. Thedirection of the second secondary flow is opposite to the direction of the main secondary flow. Thisflow pattern is evident from the middle sections of the first half of the bend up to the end of the bend.The results of flow pattern and bed scour were also addressed. In addition, the vortices in the bend, thechanges in the secondary flow and the vortices and the scour pattern at the outer bank andsedimentation at the inner bank are investigated.}, keywords = {}, title_fa = {مطالعه آزمایشگاهی الگوی جریان سه بعدی و آبشستگی در قوس 90 درجه}, abstract_fa = {}, keywords_fa = {}, url = {https://jhyd.iha.ir/article_85473.html}, eprint = {https://jhyd.iha.ir/article_85473_d9a24f4e004583aed12d01f22704c6d2.pdf} } @article { author = {Abbasi, A. and Sabbagh-Yazdi, S.R.}, title = {Upwind Finite Volume Solution of Water Hammer in Pipes without Column Separation in Unsteady Friction Model}, journal = {Journal of Hydraulics}, volume = {3}, number = {3}, pages = {59-65}, year = {2008}, publisher = {Iranian Hydraulic Association}, issn = {2345-4237}, eissn = {2645-8063}, doi = {10.30482/jhyd.2008.85474}, abstract = {The waves resulting from instantaneous and complete valve-closure in pressurized pipe systems,propagate upstream and/or downstream in the hydraulic system .The pressure (head) and velocity ofthe flow (waves) are important parameters in the design of pipeline systems. A simple and efficientapproximation to the Vardy–Brown unsteady friction equation is implemented within a FVM solutionfor unsteady pipe flows. The model is compared with measured data and numerical data produced by atwo-dimensional turbulence water-hammer model. The results show that the model is in goodagreement with both laboratory and numerical results. The computed minimum and maximum valuesand the time period of the pressure waves are in close agreement with the 2-D numerical solution andexperimental measurements.}, keywords = {}, title_fa = {اصطکاک ناماندگار در تحلیل حجم محدود جهتمند پدیده ضربه قوچ در لوله ها در شرایط عدم جدایی توده آب}, abstract_fa = {}, keywords_fa = {}, url = {https://jhyd.iha.ir/article_85474.html}, eprint = {https://jhyd.iha.ir/article_85474_d21ad8d526652d521e8c025cf844f38a.pdf} } @article { author = {}, title = {English Abstract}, journal = {Journal of Hydraulics}, volume = {3}, number = {3}, pages = {69-73}, year = {2008}, publisher = {Iranian Hydraulic Association}, issn = {2345-4237}, eissn = {2645-8063}, doi = {10.30482/jhyd.2008.85475}, abstract = {}, keywords = {}, title_fa = {چکیده های انگلیسی}, abstract_fa = {}, keywords_fa = {}, url = {https://jhyd.iha.ir/article_85475.html}, eprint = {https://jhyd.iha.ir/article_85475_b3e0496bf088c579499c2b538b7132c6.pdf} }