Flow For Re Research Articles

An experimental investigation of the swirling flow in a tall-form counter current spray dryer

This work studies the air flow in a large swirl counter-current dryer using sonic anemometry. Air velocity and turbulence fields are reported at isothermal conditions and in the absence of particles. In a tall-form unit the structure of the flow is largely influenced by the design of the exit. A contraction originates a central jet and suppresses the formation of recirculation zones despite the vortex acquires a high swirl intensity Ω (i.e. 1<Ω<2). Access to a full scale tower has permitted to: (a) identify asymmetries owed to the design of inlet and exhaust ducts, (b) present the first detailed turbulence data in production units, characterized by a highly anisotropic field and the axial decay of the turbulence kinetic energy, (c) study the flow stability, identifying the precession of the vortex core and oscillations at a constant Strouhal number and (d) study the impact that a rough wall has in the strength of the swirl. This work presents the first clear evidence of significant friction in spray dryers. The swirl intensity Ω decays exponentially in the dryer at a rate between 0.08 and 0.09, much higher than expected in pipe flow and independent of Re in the range 105–2.2⋅105. Production dryers have a large characteristic wall roughness due the presence of deposits, which explains the stronger friction and the discrepancies found in the past between data at full scale or clean laboratory or pilot scale units. It is essential to address this phenomenon in current numerical models, which are validated on laboratory or pilot scale facilities and ignore the role of deposits, thus causing an overprediction of the tangential velocity above 30–40%.

Experimental Study of Flow Structures around Side-by-Side Spheres

The flow characteristics of a single and the two side-by-side spheres immersed in a uniform flow for Re = 5 × 103 are studied qualitatively and quantitatively employing dye visualization and a part...

Suppression of vortex shedding on a bluff body

Previous experimental observations suggest that a moving ground can be numerically simulated avoiding vorticity generation on it. In this research line the current paper presents a two-dimensional Lagrangian Vortex Method, which is able to analyze the vortex shedding suppression on a circular cylinder near a moving ground in a high Reynolds number flow of Re=1.0×105. The main purpose is to utilize numerical results to construct the instantaneous velocity and pressure fields for this kind of unsteady viscous flow. The analyses demonstrate that the physical mechanisms involved are associated with an additional circulation caused by the fluid viscosity and with the Venturi effect. Both of these effects are responsible for the increase in lift force as well as for the decrease in drag force acting on body surface.

대기압 플라즈마 제트의 기체 유량에 대한 방전 특성

대기압 플라즈마 제트 장치의 유량 변화에 대한 플라즈마 방전 특성을 실험적으로 조사하고 이를 유체역학적으로 해석하였다. 유리관에 주입되는 아르곤 기체의 유량 변화에 대한 레이놀즈 수(Re)로 결정되는 기체 흐름의 형태 변화와 베르누이 정리에 의한 압력 변화가 플라즈마 발생에 영향을 준다. 유리관 내부에 발생하는 플라즈마의 길이 변화의 실험을 통하여, 아르곤 기체에 대한 레이놀즈 수가 Re<2,000이면 층류이고, Re>4,000이면 난류가 형성된다. 이는 일반 유체에서 알려진 결과와 일치한다. 층류에서 유량의 증가로 플라즈마의 길이가 증가한다. 층류와 난류의 전환 영역에서 플라즈마의 길이는 줄어든다. 난류 영역에서는 방전 기체의 흐름이 불규칙함으로서 방전 경로가 흐트러져 플라즈마 칼럼의 길이가 매우 짧아지고 급기야 플라즈마가 소멸된다. 층류에서 주입 유량의 증가로 유리관 내의 유속이 증가하면, 베르누이 정리에 의하여 유리관 내부의 압력이 낮아진다. 관내의 압력이 낮아지면, 파센 법칙에 의하여 관내의 전기장의 세기가 증가하여 방전 전압이 낮아진다. 따라서 주입 유량이 증가하면, 동일한 구동 전압에서 유리관에 발생하는 플라즈마의 길이는 길어진다. 층류의 방전은 유리관 밖에서도 층류의 흐름이 일정 길이로 유지되므로 시료 표면에 조사되는 플라즈마 빔의 직경은 유리관의 직경 이하로 유지된다. The influence of gas flow on the plasma generation in the atmospheric plasma jet is described with the theory of hydrodynamics. The plasma discharge is affected by the gas-flow streams with Reynolds number (Re) as well as the gas pressure with Bernoulli's theorem according to the gas flow rate inserted into the glass tube. The length of plasma column is varied with the flow types such as the laminar flow of Re<2,000 and the turbulent flow of Re>4,000 as it has been known in a general fluid experiments. In the laminar flow, the plasma column length is increased as the increase of flow rate. Since the pressure in the glass tube becomes low as the increase of flow velocity by the Bernoulli's theorem, the breakdown voltage of plasma discharge is reduced by the Paschen's law. Therefore, the plasma length is increased as the increasing flow rate with the fixed operation voltage. In the transition of laminar and turbulent flows, the plasma length is decreased. When the flow becomes turbulent as the flow rate is increasing, the plasma length becomes short and the discharge is shut down ultimately. In the discharge of laminar flow, the diameter of plasma beam exposed on the substrate surface is kept less than the glass diameter, since the gas flow is kept to the distinct distance from the nozzle of glass tube.

Characteristics of integrated micro packed bed reactor-heat exchanger configurations in the direct synthesis of dimethyl ether

The performance of three integrated micro packed bed reactor-heat exchangers (IMPBRHEs) for direct DME synthesis over physical mixtures of CuO–ZnO–Al2O3 and γ-Al2O3 catalysts was experimentally investigated. Systematic variations in reactor and slit dimensions and configuration were analyzed in terms of thermal behaviour, mass transfer, pressure drop and residence time distribution (RTD). The pressure drop was always small (<0.12bar) relative to the total pressure (50bar), and linear dependence with GHSV confirms the predicted laminar flow for Re=0.1–2. A narrow RTD was estimated by the dispersion analysis. Careful temperature measurements confirmed that the reaction temperature is mainly controlled by the oil heat exchange to give a practically uniform temperature profile for set inlet oil temperatures of 220–320°C. The micro packed beds were found free of the internal as well as external mass transfer limitations, as showed by no significant change in the CO conversion and DME yield for different catalyst particle sizes, no effect of varying the linear gas velocity, and no effect of manipulating reactant diffusion coefficient. Packed bed microstructured reactors hence provide an isobaric and isothermal environment free from transport limitations for the direct DME synthesis, in the kinetic regime as well as at equilibrium conversion.

Alfvén Mach number and IMF clock angle dependencies of sunward flow channels in the magnetosphere

[1] Interplanetary coronal mass ejections associated with strong interplanetary magnetic field (IMF) By have been shown to enhance the neutral density in low Earth orbit. The enhancement has been linked to strong downward Poynting fluxes embedded within ionospheric channels of significant sunward ExB drift (2000–3000 m/s). Here we present MHD results describing the magnetospheric counterpart of the ionospheric flow channel that Defense Meteorological Satellite Program (DMSP) encountered on 15 May 2005. It is shown that the clock angle of maximum sunward flow (θFC) depends on the IMF clock angle θFC = α * θIMF − 1.3° with α = (0.30, 0.38, 0.43, 0.45) at X = (4, 2, 0, −2) RE. This is poleward of the magnetic null point region. The flow also depends on the solar wind Alfvén Mach number Vx = Vx0 − δv * MA. The critical MA = Vx0 / δV for Vx = 0 decreases from MA = 3.42 (X = 4 RE) to MA = 2.40 (X = −2 RE). The low MA and θIMF conditions that characterized the X = 2 RE flow and resulted in strong Poynting flux occurred for 16% of all 167 h in 1998–2008 with Dst < −180 nT.

Effects of flow unsteadiness on the wall shear stress

Measurements were performed on pulsating fully turbulent flows in a pipe test rig with a diameter of 100 mm. Sinusoidal oscillatory flow at different frequencies was superimposed on a mean flow of averaged Reynolds number Re=20000 based on the pipe diameter. The measurements have been performed at different forcing frequencies (0.001 < ω+ < 0.08) covering all the oscillatory regimes; quasi-steady, relaxation, quasi laminar and high frequency. The amplitude of the flow oscillation was small enough to allow a linear response in the measurements, i.e., all flow parameters showed an oscillatory behavior at the frequency of the flow. The amplitude of the oscillatory flow was about 10% of the mean velocity in all cases. The results include mean and phase averaged values of different parameters. The centerline velocity was measured by a 2D LDA system. Hot film and constant temperature anemometry system was used to determine the wall shear stress. Bulk velocity and pressure gradient along the pipe were also acquired. The results showed a good agreement with the previous analytical, experimental and numerical results available in the literature.

Highly Unidirectional Emission and Ultralow‐Threshold Lasing from On‐Chip Ultrahigh‐Q Microcavities

Prominent examples are whispering gallery mode (WGM) microcavities, [ 2 , 3 ] which confi ne photons by means of continuous total internal refl ection along a curved and smooth surface. The long photon lifetime (described by high Q factors), strong fi eld confi nement, and in-plane emission characteristics make them promising candidates for novel light sources [ 4–9 ] and biochemical sensors with the ability of detecting few or even single nanoparticles. [ 10 , 11 ] The principal disadvantage of circular WGM microcavities is their intrinsic isotropy of emission due to their rotational symmetry. In addition to the photonic structures consisting of two or more perfectly spherical microcavities, [ 12 ] one of vital solutions is to use deformed microcavities by breaking the rotational symmetry, [ 13–16 ] which can provide not only the directional emission but also the effi cient and robust excitation of WGMs by a free-space optical beam. [ 17–20 ] Deformed microcavities fabricated on a chip are particularly desired for high-density optoelectronic integration, but they suffer from low Q factors in experiments. The Q factors are typically around or even smaller than ten thousand [ 21–27 ] limited by the large scattering losses from the involuntary surface roughness. The high Q factor is of great importance in fundamental studies and on-chip photonic applications. Here, with a pattern transfer technique and a refl ow process ensuring a nearly atomic-scale microcavity surface, we demonstrate experimentally on-chip undoped silica deformed microcavities which support both nearly unidirectional emission and ultrahigh Q factors exceeding 100 million. Consequently, low-threshold, unidirectional microlasing in such a microcavity with Q factor about 3 million is realized by erbium doping and a convenient free-space excitation.

Finite element based heatline approach to study mixed convection in a porous square cavity with various wall thermal boundary conditions

A penalty finite element method based simulation is performed to analyze the influence of various walls thermal boundary conditions on mixed convection lid driven flows in a square cavity filled with porous medium. The relevant parameters in the present study are Darcy number ( Da = 10 −5 − 10 −3), Grashof number ( Gr = 10 3 − 10 5), Prandtl number ( Pr = 0.7–7.2), and Reynolds number ( Re = 1–10 2). Heatline approach of visualizing heat flow is implemented to gain a complete understanding of complex heat flow patterns. Patterns of heatlines and streamlines are qualitatively similar near the core for convection dominant flow for Da = 10 −3. Symmetric distribution in heatlines, similar to streamlines is observed irrespective of Da at higher Gr in natural convection dominant regime corresponding to smaller values of Re. A single circulation cell in heatlines, similar to streamlines is observed at Da = 10 −3 for forced convection dominance and heatlines are found to emanate from a large portion on the bottom wall illustrating enhanced heat flow for Re = 100. Multiple circulation cells in heatlines are observed at higher Da and Gr for Pr = 0.7 and 7.2. The heat transfer rates along the walls are illustrated by the local Nusselt number distribution based on gradients of heatfunctions. Wavy distribution in heat transfer rates is observed with Da ⩾ 10 −4 for non-uniformly heated walls primarily in natural convection dominant regime. In general, exponential variation of average Nusselt numbers with Grashof number is found except the cases where the side walls are linearly heated. Overall, heatlines are found to be a powerful tool to analyze heat transport within the cavity and also a suitable guideline on explaining the Nusselt number variations.

Quantifying Turbulent Wall Shear Stress in a Stenosed Pipe Using Large Eddy Simulation

Large eddy simulation was applied for flow of Re=2000 in a stenosed pipe in order to undertake a thorough investigation of the wall shear stress (WSS) in turbulent flow. A decomposition of the WSS into time averaged and fluctuating components is proposed. It was concluded that a scale resolving technique is required to completely describe the WSS pattern in a subject specific vessel model, since the poststenotic region was dominated by large axial and circumferential fluctuations. Three poststenotic regions of different WSS characteristics were identified. The recirculation zone was subject to a time averaged WSS in the retrograde direction and large fluctuations. After reattachment there was an antegrade shear and smaller fluctuations than in the recirculation zone. At the reattachment the fluctuations were the largest, but no direction dominated over time. Due to symmetry the circumferential time average was always zero. Thus, in a blood vessel, the axial fluctuations would affect endothelial cells in a stretched state, whereas the circumferential fluctuations would act in a relaxed direction.

Determination of laminar and turbulent flow ranges through vertical packed beds in terms of particle friction factors

Despite the presence of a variety of studies dealing with the magnitude of particle Reynolds number, Re p defining transition from laminar to turbulent regime for flow through packed beds, the manner is still one of the unknowns. An approach based on the experimental data concerning upward airflow through fixed cylindrical packed beds is presented in this paper. The utilized packed beds had the following ranges of; sphericity, Φ, 0.55 ⩽ Φ ⩽ 1.00, packing material diameter to bed length ratio, D p/ L, 0.04 ⩽ D p/ L ⩽ 0.72, and bed porosity, ε, 0.36 ⩽ ε ⩽ 0.56. The test cases covered the ranges of particle Reynolds number, Re p 708 ⩽ Re p ⩽ 7772 and particle Froude number; Fr p 2.86 ⩽ Fr p ⩽ 10.39. The measurements of pressure drop through packed bed; Δ P Bed and superficial mean exit velocity; U are used to determine bed frictional effects in reference to the available literature on particle friction factors, f p. The magnitude of Re p defining transition is assumed to be 2000 with particular emphasis to the flow dynamics. The definitions of Bird et al. [R.B. Bird, W.E. Stewart, E.N. Lightfoot, Transport Phenomena , John Wiley and Sons, NY, 1960] are used to calculate f p. The calculated f p for the covered test cases are given as a function of pressure coefficient, Δ P* and Re p, Fr p, Φ, ε, D p/ L in the approximate ranges of laminar and turbulent flow for Re p < 2000 and Re p > 2000, respectively. The proposed separate equations of f p = f p(Δ P*, Re p, Fr p, Φ, ε, D p/ L) are satisfied for laminar and turbulent flows with corresponding average error margins of ±7.6% and ±18%. Furthermore ranges of transitional and fully rough flow through packed beds are estimated as 2000 ⩽ Re p ⩽ 4000 and Re p > 5000 with an analogy to the well-known Moody Chart in pipe flows.

Lead-free soldering: Materials science and solder joint reliability

Since the National Electronics Manufac tu r ing Initiative recommended Sn3.9Ag-0.6Cu for refl ow soldering and Sn-3.5Ag and Sn-0.7Cu for wave soldering in 2000, great effort has been made to address the reliability issues of lead-free soldered packages. Investigation of the dependence of properties of bulk solder alloys on compositions and processes can, of course, greatly help reliability engineering of solder joints. However, because of the strong effect of the interface between solder and soldered metal on the reliability of fi ne pitch solder joints, research of bulk solders is not enough to answer all the questions. The infl uences of composition and microstructure of solder joints on the reliability of bond interface should also be studied. In this issue, fi ve papers address materials issues directly related to solder joint reliability. In the fi rst paper, I. Dutta et al. summarize their research in characterization of microstructural coarsening in Sn-Ag based solders and its effects on mechanical properties of bulk solder as well as reliability of solder joints. In the eutectic SnAgCu alloy, the volume fraction of Cu 6 Sn 5 is much smaller than that of Ag 3 Sn and Cu 6 Sn 5 coarsens more rapidly than Ag 3 Sn. Therefore, Ag 3 Sn is the major contributor to the effects of coarsening on mechanical properties of SnAgCu solders and reliability of joints. The data indicate that a lower rate of interfacial failure of solder joints can be expected if electronic devices are handled with greater caution in the fi rst several days after assembly. The second paper by F. Guo et al. is Lead-free Soldering: Materials Science and Solder Joint Reliability

Vortex-induced vibrations of a circular cylinder at low Reynolds numbers

Results are presented for a numerical simulation of vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m* = 10) in the laminar flow regime (60 &lt; Re &lt; 200). The natural structural frequency of the oscillator, fN, matches the vortex shedding frequency for a stationary cylinder at Re = 100. This corresponds to fND2/ν = 16.6, where D is the diameter of the cylinder and ν the coefficient of viscosity of the fluid. A stabilized space–time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. Unlike at high Re, where the cylinder response is known to be associated with three branches, at low Re only two branches are identified: ‘initial’ and ‘lower’. For a blockage of 2.5% and less the onset of synchronization, in the lower Re range, is accompanied by an intermittent switching between two modes with vortex shedding occurring at different frequencies. With higher blockage the jump from the initial to lower branch is hysteretic. Results from free vibrations are compared to the data from experiments for forced vibrations reported earlier. Excellent agreement is observed for the critical amplitude required for the onset of synchronization. The comparison brings out the possibility of hysteresis in forced vibrations. The phase difference between the lift force and transverse displacement shows a jump of almost 180° at, approximately, the middle of the synchronization region. This jump is not hysteretic and it is not associated with any radical change in the vortex shedding pattern. Instead, it is caused by changes in the location and value of the maximum suction on the lower and upper surface of the cylinder. This is observed clearly by comparing the time-averaged flow for a vibrating cylinder for different Re. While the mean flow for Re beyond the phase jump is similar to that for a stationary cylinder, it is associated with a pair of counter-rotating vortices in the near wake for Re prior to the phase jump. The phase jump appears to be one of the mechanisms of the oscillator to self-limit its vibration amplitude.

D113 マイクロバブルチャネル乱流における気泡径の壁面摩擦低減現象に及ぼす影響(混相流1)

The phenomenon of skin friction reduction with micro bubble has been studied experimentally. We reveal the relation between drag reduction and the bubble size, using two different types of bubble. One is large bubble of millimeter order by porous plate ; and the other is small bubble of micrometer order made by mixing air and water under high pressure. Bubble diameter is calculated from images captured by high speed camera and the shear stress is measured by shear stress sensor. The experiments have been carried out for large bubble flow conditions with Reynolds number ranging from 10,000 to 50,000 ; void fraction up to 0.04 and small bubble flow with Reynolds number ranging from 30,000 to 50,000 ; void fraction less than 0.01. In the case of large bubble flow for Re>30,000, drag has been reduced up to 10%. In contrast, small bubbles hardly contribute to reduce shear stress due to dispersion of bubbles in turbulent channel flow.

Numerical investigation of hydrodynamics and mass transfer for in-line fiber arrays in laminar cross-flow at low Reynolds numbers

In this work, mass transfer at the shell side of an in-line hollow fiber array subjected to cross-flow is simulated by applying the domain decomposition method combined with orthogonal grid generation. Two-dimensional Navier–Stokes equations written in stream function–vorticity variables, were separately solved along with a species conservation equation for different arrays. The main factors influencing the concentration fields, local mass transfer rates and global mass transfer rates in the laminar flow of Re = 10 –200 and Pe = 10 –300 with pitch to tube diameter ratios of 1.45, 1.50, 1.75, 1.85 and 2.00 are discussed in detail. Mass transfer correlations obtained from the numerical simulations show good agreement with typical empirical correlations proposed earlier.

Parallel-multigrid computation of unsteady incompressible viscous flows using a matrix-free implicit method and high-resolution characteristics-based scheme

A three-dimensional parallel unstructured non-nested multigrid solver for solutions of unsteady incompressible viscous flow is developed and validated. The finite-volume Navier–Stokes solver is based on the artificial compressibility approach with a high-resolution method of characteristics-based scheme for handling convection terms. The unsteady flow is calculated with a matrix-free implicit dual time stepping scheme. The parallelization of the multigrid solver is achieved by multigrid domain decomposition approach (MG-DD), using single program multiple data (SPMD) and multiple instruction multiple data (MIMD) programming paradigm. There are two parallelization strategies proposed in this work, first strategy is a one-level parallelization strategy using geometric domain decomposition technique alone, second strategy is a two-level parallelization strategy that consists of a hybrid of both geometric domain decomposition and data decomposition techniques. Message-passing interface (MPI) and OpenMP standard are used to communicate data between processors and decompose loop iterations arrays, respectively. The parallel-multigrid code is used to simulate both steady and unsteady incompressible viscous flows over a circular cylinder and a lid-driven cavity flow. A maximum speedup of 22.5 could be achieved on 32 processors, for instance, the lid-driven cavity flow of Re = 1000. The results obtained agree well with numerical solutions obtained by other researchers as well as experimental measurements. A detailed study of the time step size and number of pseudo-sub-iterations per time step required for simulating unsteady flow are presented in this paper.

UNSTEADY FLOW AND HEAT TRANSFER IN PARALLEL-PLATE HEAT EXCHANGERS WITH IN-LINE AND STAGGERED ARRAYS OF POSTS

A numerical study has been carried out to analyze the unsteady three-dimensional flow and conjugate heat transfer in a channel with in-line and staggered arrays of periodically mounted square posts. The simulations have been carried out for Reynolds numbers in the range 150–600 (based on the post width and the average velocity), and a Prandtl number of 6.99 (corresponding to water). The flow is found to be unsteady at a critical Reynolds number around 400 for the in-line case, while it is unsteady at Re = 150 (the lowest Reynolds number studied) for the staggered case. The unsteady flow shows quasi-periodic behavior with multiple frequencies (having different dominant shedding frequencies). For the in-line configuration, the heat transfer enhancement is small when the flow is steady (2.28–2.88 relative to a plane channel flow for Re ≤ 250), but it is significant when the flow is unsteady (17 times that for a plane channel flow for Re = 600). The staggered case shows significant enhancement at all Reynolds number (19–66), but with an associated pressure loss penalty (54–150 times the value for the plane channel flow). However, the thermal performance factor for the in-line configuration has lower values than the staggered configuration at all Reynolds numbers.

An experimental study on swirling flow in a 90 degree circular tube by using particle image velocimetry

The study of swirl flow is of technical and scientific interest because it has an internal recirculation field, and its tangential velocity is related to the curvature of the streamline. The fluid flow for tubes and elbows of heat exchangers has been studied largely through experiments and numerical methods, but studies about swirl flow have been insufficient. Using the Particle Image Velocimetry method, this study found the time averaged velocity distribution, time averaged turbulence intensity with swirl and without swirl flow for Re = 10,000, 15,000, 20,000 and 25,000 along longitudinal sections, and the results appear to be physically reasonable. In addition, streamwise mean velocity distribution was compared with those of Khodadai et al. and Jeong et al.

Bluff-body Wake Evolution And Interaction In Two Dimensions

disordered structures in the far wake. unknown Features of the interaction of 2D wakes, such as coupling between the onset of the second wake to scale with Re-’”. Finally, we present previously flows, it persists to Re>1200. We find the dimensionless downstream distance to wake), which exists in 3D only for low Reynolds numbers (Rec300).In soap film striking feature of the far wake is the onset of the secondary vortex street (second the cylinders (far wake region) and interaction of multiple wakes. The most driven instabilities. We also examine the features of 2D wakes far downstream of dependence of St upon Re to weaken at higher Re is attributable entirely to shearremains valid for 2D data. In the absence of 3D effects, the trend of the not describe the behaviour of 3D flow for higher Re, however, we show that it from 2D. A recently developed fit for St in terms of Ree”’ valid For Re-480 does neutrally stable to spanwise perturbations and thus not substantially different Reynolds number Re due to spanwise instabilities. For Re<lSO, the 3D flow is dimensionless vortex-shedding frequency (the Strouhal number St) upon the In 2D, there is no evidence of discontinuities in the dependence of the between the wake parameters in two- and three- dimensional (2D and 3D) wakes. with cylinder wakes in a nearly two-dimensional soap film flow show differences such important parameters as the vortex-shedding frequency? Our experiments cylinder axis. What is the respective influence of the Former and the latter upon cylinder wake, instabilities develop in directions normal and parallel to the however, many issues related to wake instabilities still need elucidation. For a Bluff-body wakes have been extensively studied for more than a century,

Rice (Oryza sativa)-based farming systems for livelihood improvement of Indian farmers

Farming system research is a multi-disciplinary holistic approach to solve the problems of small and marginal farms. Small and marginal farmers are the core of the Indian rural economy constituting 80% of the total farming community but possessing only 36% of the total operational land. The declining trend of per caput land availability poses a serious challenge to the sustainability and profitability of farming. Under such conditions, it is appropriate to integrate land-based enterprises, viz. dairy, fishery, poultry, duckery, apiary, field and horticultural crops within the farm, with the objective of generating adequate income and employment for these small and marginal farmers and thereby improved livelihoods. The production system adopted during Green Revolution has been explorative and the natural resources like soil and water were subjected to immense pressure beyond carrying capacity. As a result sustainability of agricultural production system and the farming system is in crises. This suggests the urgent need of integrated farming system development where the various components of the farming system may be in- tegrated to improve productivity and profitability as well as resource conservation along with maintenance of the environment. Rice ( Oryza sativa L.) occupies a position of overwhelming importance in Asian agriculture and it constitutes the bulk of the Asian diet. For many people in the poor countries, rice is the main source of energy, and it plays an important role in providing livelihood to the Asian population. It is largely grown in Asia (90% area) under diverse conditions of soil, climate, hydrology and topography. Rice farming is the single most important source of employment and income for the majority of rural people in these regions. Among the various farming system options in rice ecologies, rice fish farming has great potential particularly in eastern India in view of the resources, food habits and other socio-economic conditions. Ricefish diversified farming system with the integra- tion of compatible components, such as improved varieties of rice, fish, prawn, pulses, oilseeds, horticultural crops, agroforestry, mushroom, poultry, duckery, goatery, floriculture, apiculture etc. can increase the farm pro- ductivity, besides farm employment over traditional rice farming. There exist chain of interactions and flow of re- sources among the different enterprises in a integrated farming system. To make farming profitable and improve resource use efficiency at the farm level, the synergy among interacting components of farming system needs to be exploited. In this paper focus is on different aspect of rice-based farming system involving methodology, deter- minants, and forms of rice-based farming systems and their impact on livelihood of farming communities.