Capturing of transition by the RNG based algebraic turbulence model

Abstract

This paper concerns the RNG based algebraic turbulence model. This model has characteristics to capture transitional process from laminar to turbulent flow. This is determined by the argument of the Heaviside function, which becomes a threshold for the occurrence of turbulence. It is supposed that proper modeling of this argument will lead to correctly capture transition location. In the present paper, this argument is modeled in such a way that the form of cubic equation for the turbulent kinematic viscosity be maintained. Moreover, the length scale which is required to calculate the turbulent kinematic viscosity is newly proposed, taking into account the freestream pressure gradient. The validation is performed by comparing the calculated results with the empirical expressions as well as the experimental data. This model can simulate the streamwise intermittency effect, by which a sudden increase of skin friction is prevented. Moreover, the transition location can be predicted within reasonable accuracy compared with the experimental data.

(Yoshiaki Nakamura and Andi Eka Sakya. An International Journal Computers & Fluids, Volume 24 Number 8, November 1995. ISSN: 0045-7930. page 909-918)

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Transfer of technology within the establishment of InaTEWS

Following the high magnitude earthquake that generated a gigantic tsunami in Aceh in 2004, the Indonesian government initiated work to develop the Indonesia Tsunami Early Warning System (InaTEWS). The work aimed to develop a system that would disseminate a warning within 5 minutes all over Indonesia. The State Ministry of Research and Technology (Ristek) developed the system in co-ordination with several institutions. InaTEWS, inaugurated on 11 November 2008, is being used as part of daily operations by the Agency for Meteorology Climatology and Geophysics. This transfer of technology has enabled the InaTEWS to warn about the occurrence of natural disasters, such as earthquakes and Tsunami, within five minutes via the 5-in-1 system to authorities all over Indonesia.

This paper discusses the process of development approach used in the work.

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Evaluation of an RNG-based algebraic turbulence model

Abstract

A new length scale and dissipation rate for a purely mathematically based algebraic turbulence model derived from renormalization group theory is proposed. The proposed length scale is developed in conjunction with an accurate characteristic length scale and the dissipation rate pertaining to the damping action due to the viscous force. In the fundamental aspect, this model is tested by applying it to a flat-plate problem to check that a simple shear layer is modeled adequately. As an application, a typical transonic flow around an airfoil is presented together with the experimental results. Comparison with other algebraic turbulence models is discussed.

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Hukum Tabur Tuai

Rekan-rekan semua, 

Setiap kali memperingati HUT Kemerdekaan, setiap kali saya tercenung pada lagu kebangsaan kita: BANGUNLAH JIWANYA, BANGUNLAH BADANNYA, UNTU INDONESIA RAYA. 

Ijinkan saya mengutip cerita di bawah, dari BBG. 


"HUKUM TABUR TUAI" 


Seorang CEO hendak mewariskan perusahaan besar kepada karyawan terbaiknya. 
Untuk itu ia memanggil seluruh karyawannya, memberikan masing² sebutir BENIH di tangannya dan berkata: "Sirami dengan teratur, rawat, dan kembalilah setahun dari sekarang dengan membawa tanaman yang tumbuh dari benih ini. Yang TERBAIK, pemiliknya akan menjadi penggantiku sebagai CEO perusahaan ini". 

Seorang karyawan, katakanlah namanya ABUNAWAS, pulang ke rumah. Setiap hari disiraminya dengan air dan pupuk. Setelah 6 bln, di kantor, eksekutif lainnya saling membicarakan tanaman mereka, sedangkan ABUNAWAS melihat TIDAK ADA PERUBAHAN yang terjadi pada benih miliknya. IA MERASA GAGAL. 

Setelah setahun, seluruh eksekutif menghadap CEO, memperlihatkan hasil benih tersebut. ABUNAWAS berkata pada istrinya bahwa ia tdk akan membawa pot yang kosong, namun istrinya mendorongnya untuk menyatakan yang sebenarnya.  ABUNAWAS menyadari bahwa istrinya menyarankan HALYANG BENAR. Memasuki ruangan meeting, ABUNAWAS membawa sebuah pot kosong. Seluruh mata memandangnya kasihan. 

Ketika Sang CEO memasuki ruangan, ia memandang keindahan seluruh tanaman itu, hingga akhirnya berhenti didepan ABUNAWAS yang tertunduk malu. Sang CEO memintanya ke depan dan menceritakan TRAGEDI yang menimpanya. 

Ketika ia selesai bercerita, Sang CEO berkata, "berikan tepuk tangan yang meriah untuk ABUNAWAS, CEO yang baru". Ia berkata, “Aku memberikan kepada kalian sebutir benih yang sebelumnya TELAH KUREBUS DI AIR PANAS hingga mati dan tidak mungkin untuk tumbuh. Melihat bahwa benih itu tidak tumbuh, kalian menukarnya dan berbohong kepadaku. Lain halnya dengan ABUNAWAS, dia mau berkata yg sebenarnya terjadi. 

 (y) Tabur KEJUJURAN, tuai KEPERCAYAAN 
 (y) Tabur KETEKUNAN, tuai KEMENANGAN 
 (y) Tabur KERJA KERAS, tuai KESUKSESAN... 

Dirgahayu Republik tercinta. 

Salam dan sukses selalu. 

AES 

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Salam Pembuka

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