Ezgi AKBUDAK, Bülent YANIKTEPE, Ertuğrul ŞEKEROĞLU, Ömer KENAN, Muammer OZGOREN

Torpido Benzeri Geometrilerin İki Tandem Düzenlemesi İçin Akış Yapılarının İncelenmesi

Otonom sualtı araçları ile ilgili deneysel çalışmalar torpido benzeri bir geometri için literatürde sınırlıdır. Bu çalışmada, çeşitli aralıklarla tek ve çift tandem düzenlemesi için uzunluk-çap en boy oranı L/D=5 olan, eliptik bir burna ve konik kıç kısmına sahip aerodinamik torpido benzeri bir geometrinin akış yapıları, bir kapalı çevrim su kanalı içinde Parçacık Görüntülemeli Hız ölçme (PIV), yöntemi kullanılarak incelenmiştir. Geometrinin uzunluğu için tanımlanan Reynolds sayısı (L=200 mm) Re=20000 değeri, serbest su akış hızı 100 mm/s, olarak alındı, iki özdeş torpido benzeri geometri arasındaki mesafe (G) 0-120 mm aralığında değiştirildi. Torpido benzeri geometrinin tüm konfigürasyonları için anlık ve 1000 görüntüden hesaplanan zaman ortalamalı karşılaştırmalı olarak sunuldu. Boyutsuz boşluk oranlarına (G/L) 0 ila 0,6 arasındaki bağlı tandem düzenlemelerinin, anlık hız alanı (V), zaman ortalamalı hız alanı , boyutsuz akış yönündeki hız bileşeni ve akım çizgisi topolojilerinin <> tek torpido benzeri geometriden önemli ölçüde farklı olduğu gösterilmiştir. Öndeki modelin firar ucu arkadaki modelin burnuna temas durumu için arka geometrinin art izi bölgesi tek model art izine benzer, ancak tüm zaman ortalamalı akış yapıları uzamakta ve simetrik akış yapıları biraz deforme olmaktadır. Boyut boşluk 0,15≤G/L≤0,30 aralık oranları için iki model arasında akış alanı sağlandığında, öndeki geometriden ayrılmış akış yapılarının arkadaki geometrinin burnuna çarpması nedeniyle karmaşık ve dönümlü akış yapıları oluşur. Boşluk oranı en büyük değer G/L=0,6'ya yükseldikçe hem tekli hem de art arda düzenlemesinin art izi bölgesi hemen hemen aynı hale gelir. İncelenen torpido benzeri geometrinin akış özellikleri için daha ayrıntılı bilgi, bu çalışmadaki PIV sonuçlarıyla doğrulama yapıldıktan sonra hesaplamalı akışkanlar dinamiği kullanılarak belirlenebilir.

Anahtar Kelimeler:

Eliptik burun, PIV, Tandem düzenleme, Torpido benzeri geometri, Türbülanslı akış, Viskoz akış

Investigation of the Flow Structures for Two Tandem Arrangement of Torpedo-Like Geometries

Experimental studies on autonomous underwater vehicles for a torpedo-like geometry are limited in the literature. In this study, flow structures of a streamlined torpedo-like geometry having an elliptical nose and tampered stern at a length to diameter aspect ratio of L/D=5 for a single and double tandem arrangement with various spacings have been investigated using Particle Image Velocimetry (PIV) method in a closed loop water channel. Reynolds number defined for length of the geometry (L=200 mm), free stream water velocity of 100 mm/s was taken as Re=20000, the spacing (G) between two identical torpedo-like geometries is changed from 0 to 120 mm. Instantaneous 1000 images and their time-averaged results are comparatively presented for all configurations of the torpedo-like geometry. It is demonstrated that the tandem arrangements depending on the dimensionless spacing ratios (G/L) between 0 to 0.6 are significantly different from the single torpedo-like geometry for the flow patterns of instantaneous and time-averaged velocity field, dimensionless streamwise velocity component and streamline topology. For the contacting case in which the following model nose is placed on the trailing-edge of the front model, wake region of the back geometry is similar to the single model wake but the all of time-averaged flow patterns elongated and symmetrical flow patterns are slightly deformed. When flow area is provided between two models for spacing ratios of 0.15≤G/L≤0.30, chaotic and rotational flow patterns occur due to the impinging separated flow patterns from the front geometry to the nose of the downstream one. As the gap distance increases to the largest value at G/L=0.6, the wake region of both the single and tandem arrangement becomes almost identical. More detailed information for the flow characteristics of the examined torpedo-like geometry can be determined by using computational fluid dynamics after validation with PIV results in the present study.

Keywords:

Elliptical nose, PIV, Tandem arrangement, Torpedo-like geometry, Turbulent flow, Viscous flow,

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