**1. Introduction**

Stirrer geometry and design in a mechanically agitated tank have been studied over a wide range of design aiming at improving the agitation efficiency. Several studies which have already been carried out were interested in enhancing the vessel property, experimentally and numerically. In fact, the experimental study includes the effect of removal of baffles, the impeller geometrical effects, the number of blades on energy efficiency, and the impacts of solid concentration and particle size on power consumption [1]. Mixing time and pattern in the agitated vessel was also experimentally investigated at various mixing Reynolds numbers [2]. Three types of impellers generated in different liquid flows as well as their position were used to investigate their influences on the kinetic parameters in a batch cooling crystallizer [3]. In addition, particle image velocimetry technique (PIV) was used to carry out the turbulent flow inside a cylindrical baffled stirred vessel with a set of speed ranging from 100 to 350 rpm [4]. Ben Amira et al. [5] also studied the hydrodynamic structure of the flow generated by eight concave blade turbines. Furthermore, PIV technique is also used to estimate the turbulence energy dissipation rate in a stirred vessel generated by a Rushton turbine [6]. In addition, both experimental and numerical techniques were developed simultaneously. In fact, Cruz-Díaz et al. [7] modeled the operation of the FM01-LC reactor coupled with a continuous stirred tank (CST) in recirculation mode. Li et al. [8] used the large eddy simulation and the PIV technique to calculate the velocity field generated by a Rushton turbine. In-line high shear mixers (HSMs) with double rows of ultrafine inclined stator teeth were experimentally and numerically investigated under different rotor speeds and flow rates [9]. Furthermore, computational fluid dynamics (CFD) simulations were used to investigate the effects of impeller configuration on fungal physiology and cephalosporin C production by an industrial strain *Acremonium chrysogenum* in a bioreactor equipped with conventional and novel impeller configuration, respectively [10]. Navier-Stokes equation in conjunction with the RNG (renormalization group) of the k-ε turbulent model was used to study the turbulent flow induced by the six flat blade turbines (FBT6), the Rushton turbine (RT6), and the pitched blades turbine (PBT6) in a stirred tanks [11]. Finite volume method was employed to solve the Navier-Stokes equations governing the transport of momentum to compare four different turbulence models used for numerical simulation of the hydrodynamic structure generated by a Rushton turbine in a cylindrical tank [12]. Multiple impellers were used in a stirred vessel to form the micro/nano drug particle in the biopharmaceutical classification system [13].

According to the biography, it is interesting to study the effect of the blade shape in order to improve the hydrodynamic structure. In this paper, we are interested in studying the hydrodynamic structure in a cylindrical stirred vessel equipped by an eight-curved blade turbine.
