An ultrasound imaging system includes a transducer array (202) with a plurality of transducer elements (206) configured to transmit a pulsed field beam into a scan field of view, receive echo signals produced in response to the pulsed field interacting with particles/structure flowing/moving in the scan field of view, and generate electrical signals indicative of the echo signals. The ultrasound imaging system further includes a beamformer (212) including multiple synthetic transmit aperture beamformers configured to process the electrical signals over a plurality of processing channels (312) into corresponding receive-beams of RF-data with a beam-level delay, channel-level delays, a beam-level gain and channel-level gains. The ultrasound imaging system further includes a velocity processor (216) configured to estimate a flow velocity of the structure flowing in the scan field of view from the RF-data. The ultrasound imaging system further includes a rendering engine (224) configured to display the flow velocity estimate on a display (226) with color-coding.