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Valve-less piezoelectric pump with hemisphere-segment group is a novel bluff-body pump,which has hemisphere-segment group as no-moving part valve.The flow-facing angle of hemisphere-segment group has a complicated influence on the flow resistance and pumping performance for the forward and reverse flow around the hemisphere-segment group.In order to optimize the pumping performance of the valve-less pump with hemisphere-segment group,the influence of the flow-facing angle of hemisphere-segment group on the flow resistance and flow rate was studied.Based on the flow resistance analysis of hemisphere-segment group with zero flow-facing angle,the empirical formulas were derived for the resistance coefficients of the hemisphere-segment group with non-zero flow-facing angle.And the flow resistance and pump flow rate were tested and validated.Meanwhile,the experiment was conducted and analyzed to find the influence of flow-facing angle on the pumping performance.During the experiment,with the driving voltage at 120V,driving frequency at 6Hz,and the flow-facing angle at 45°,the pump flow rate of 46.9mL/min was obtained.Under the same driving condition and the flow-facing angle at the delivery lift angle of 110°,the delivery lift of 78.1mm was obtained.The experiments of flow rate and delivery lift reveal that the flow-facing angle θ has impact on flow resistances both in forward and reverse flow direction,as a result,the pumping performance can be influenced.According to the research in this paper,the results are: the empirical formulas of resistance coefficients of hemisphere-segment group with non-zero flow-facing angle can be used to analyze and calculate flow resistance and theoretical pump flow rate; when the flow-facing angle θ≤45°,the pump flow rate increases along with the increasing of the flow-facing angle,and at θ≈45°,the optimum pumping performance is obtained for the first time; when 45°≤θ≤90°,the pump flow rate decreases along with the increasing of the flow-facing angle,and at θ≈180°,the pump flow rate tends to theoretical zero value.In addition,the pumping performance can be improved by appropriately increasing the row interval or reducing the column interval of hemisphere-segment group.