تخمين سرعت نسبي پيشاني جريان غليظ براي سيال پيرامون متحرك هم جهت با حركت جريان غليظ

Estimation of Relative Head Velocity of Density Current When Ambient Water Flowing in Same Direction of Density Current

جريان هاي غليظ زماني رخ مي­دهد كه سيالي درون سيال ديگر با چگالي متفاوت حركت كند. تحقيقات زيادي در زمينه بررسي جريان غليظ هنگامي كه سيال پيرامون ساكن است وجود دارد ولي در حالتي كه سيال پيرامون هم جهت با جريان غليظ در جريان است مطالعاتي انجام نشده است، لذا اين تحقيق با استفاده از يك مدل فيزيكي، فلومي به عرض 35 سانتي­متر ، طول 8/8 متر و ارتفاع 70 سانتي­متر و در نظر گرفتن جريان غليظ نمكي، سه دبي ورودي سيال پيرامون 2 ،3 و 4 ليتر بر ثانيه، سه دبي سيال غليظ 5/0، 0/1 و 5/1 ليتر بر ثانيه، سه شيب 0 ، 1 و2 درصد و سه غلظت 10، 15 و 20 گرم بر ليتر انجام شد. نتايج نشان داد كه سرعت پيشاني تابعي از سرعت سيال پيرامون مي­باشد، لذا از سرعت نسبي پيشاني در تجزيه و تحليل داده­ها استفاده گرديد. در نهايت يك رابطه به منظور تخمين سرعت نسبي پيشاني جريان غليظ ارائه شد.

Density current occurs when a fluid flowing through another fluid with different density. Lot of research can be found in the literature about density current, but in all of them one of the fluids is stationary. Since no study can be found about density current when fresh water is flowing in the same direction of density current, therefore in this research attempts are made to study this especial case with the aid of experimental flume. The experiments were conducted in a flume with 35 cm wide, 8.8 m long and 70 cm height. The dense fluid was salt water with discharges of 0.5, 1 and 1.5 L/s and the discharge of fresh water were equal to 2, 3 and 4 L/s. The concentrations of dense fluid were 10, 15 and 20 g/L, and the bed slop of the flume was 0, 1 and 2%. The results showed that the head velocity is a function of the velocity of fresh water and therefore the relative head velocity is selected for further analyses. Finally, an equation is suggested to find relative head velocity.