NEW YORK—A glance at the U.S. Open, the last Grand Slam tennis tournament of 2021: Surface Hard courts. Site USTA Billie Jean King National Tennis Center in Flushing Meadows. Schedule The 14-day tournament begins Monday. The women’s singles final is Saturday, Sept. 11; the men’s singles final is Sunday, Sept. 12. There are separate day and night sessions. Spectators Fans will be allowed back at the tournament—with no requirements to wear masks at matches but they must show proof of having at least one COVID-19 vaccine shot—a year after all spectators were banned because of the coronavirus pandemic. 2020 Women’s Singles Champion Naomi Osaka of Japan. 2020 Men’s Singles Champion Dominic Thiem of Austria. Last Year Osaka came back to beat Victoria Azarenka in the women’s final for a 1–6, 6–3, 6–3 victory to earn her second U.S. Open championship and third Grand Slam title overall (she has since added …